Aqueous polyimide precursor solution composition and method for producing aqueous polyimide precursor solution composition

ABSTRACT

An aqueous polyimide precursor solution composition in which a polyamic acid which is formed by the reaction of a tetracarboxylic acid component and a diamine component, and contains a repeating unit represented by the following formula (1), is dissolved in an aqueous solvent together with an imidazole in an amount of 1.6 mole or more per mole of the tetracarboxylic acid component of the polyamic acid, in which the aqueous polyimide precursor solution composition contains no organic solvent, and the polyamic acid has an inherent viscosity of 0.2 or more.

TECHNICAL FIELD

The present invention relates to an aqueous polyimide precursor solutioncomposition and a method for easily producing an aqueous polyimideprecursor solution composition. The aqueous polyimide precursor solutioncomposition is preferred because of having high environmentalacceptability as compared with a polyimide precursor solutioncomposition comprising an organic solvent. The production method of thepresent invention does not require any solvent other than water, andtherefore it may provide an aqueous polyimide precursor solutioncomposition having a lower content of organic solvent than theconventional compositions, and may provide an aqueous polyimideprecursor solution composition containing an aqueous solvent andcontaining no organic solvent, which has higher environmentalacceptability. In addition, a polyimide may be suitably obtained fromthe aqueous polyimide precursor solution composition. A polyimideobtained from a specific aqueous polyimide precursor solutioncomposition of the present invention, in particular, has excellentproperties such as heat resistance, mechanical strength, electricalproperties, and solvent resistance, and further has excellentflexibility.

The present invention also relates to a method for producing a polyimideseamless belt using the aqueous polyimide precursor solutioncomposition. The present invention also relates to a binder resincomposition (aqueous polyimide precursor solution composition for abinder resin) for an electrode of an electrochemical device such as alithium ion secondary battery and an electric double layer capacitor.The present Invention also relates to an aqueous polyimide precursorsolution composition for a flexible device substrate, for example, anaqueous polyimide precursor solution composition for a substrate of adisplay device such as a liquid crystal display, an organic EL displayand an electronic paper, and a light-receiving device such as alight-receiving element of a thin-film solar cell.

BACKGROUND ART

A polyimide obtained from a tetracarboxylic dianhydride and a diamine,particularly an aromatic polyimide obtained from an aromatictetracarboxylic dianhydride and an aromatic diamine has excellentproperties such as heat resistance, mechanical strength, electricalproperties, and solvent resistance, and therefore is widely used in theelectrical/electronics industrial field and the like. Because polyimideshave poor solubility in organic solvents, however, polyimides aregenerally prepared by applying a solution composition in which apolyamic acid as a polyimide precursor is dissolved in an organicsolvent, for example, onto a substrate surface, and then heating thesolution composition at a high temperature to effect dehydration/ringclosure (imidization). The polyamic acid solution composition to producea polyimide contains an organic solvent and must be subjected to heattreatment at a high temperature, and therefore the polyamic acidsolution composition is not necessarily environmentally friendly and insome cases, its application is limited.

Additionally, as described above, an aromatic polyimide obtained from anaromatic tetracarboxylic dianhydride and an aromatic diamine hasexcellent heat resistance, mechanical strength and the like, andtherefore is widely used in the electrical/electronics industrial fieldand the like. In the meantime, there is a need for a polyimide furtherhaving excellent flexibility, for example, in the binder application,flexible-device application and the like.

As for a water-soluble polyimide precursor, Patent Literature 1, forexample, proposes a process for producing an aqueous polyamide acid saltsolution composition, comprising

polymerizing a tetracarboxylic dianhydride and a diamine in an organicsolvent, to provide a polyamide acid;

optionally hydrolyzing the polyamide acid, as necessary;

pouring the resulting varnish into water, to pulverize the polyamideacid and to extract and remove a reaction solvent contained in thepolyamide acid;

drying the polyamide acid; and

reacting the polyamide acid in water with a certain amine compound suchas 2-methylamino diethanol to form a water-soluble polyamide acid salt.However, it is difficult to form a high molecular weight polymer fromthis aqueous polyamide acid salt solution composition (polyimideprecursor composition) and it is also desirable to further improve theproperties of the polyimide obtained.

Patent Literature 2 proposes a water-soluble polyimide precursorprepared by reacting a polyamic acid (polyimide precursor), which isprepared by reacting a tetracarboxylic acid component with an aromaticdiamine component in an organic solvent, with 1,2-dimethylimidazoleand/or 1-methyl-2-ethylimidazole, and then separating the water-solublepolyimide precursor from the reaction mixture. The water-solublepolyimide precursors prepared in Examples of Patent Literature 2,however, were ones from which only amorphous aromatic polyimides couldbe obtained. Although a polyimide which is obtained from thewater-soluble polyimide precursor prepared in Patent Literature 2 isamorphous and thermal-fusion bondable, and is suitably used as a binderfor a woven or nonwoven fabric made of organic or inorganic fibers,there is room for improvement in the properties of the polyimide in someapplications. Additionally, the aqueous polyimide precursor solutioncomposition is prepared by a process, comprising

preparing a water-soluble polyimide precursor in an organic solvent;

separating the water-soluble polyimide precursor therefrom; and

dissolving the separated water-soluble polyimide precursor in an aqueoussolvent.

Thus, extremely complicated operations are needed. Moreover, an organicsolvent cannot be completely removed from a water-soluble polyimideprecursor prepared in the organic solvent. (If the water-solublepolyimide precursor is heated so as to completely remove the organicsolvent, imidization occurs, and therefore the polyimide precursor losessolubility in water.) For this reason, the aqueous polyimide precursorsolution composition obtained will inevitably contain an organicsolvent.

Meanwhile, Non Patent Literature 1 shows that a binder resin forelectrodes having a lower degree of swelling in a liquid electrolyte ispreferred, because the retention of discharge capacity incharge-discharge cycles increases with the decrease in the degree ofswelling of the binder resin.

In Non Patent Literature 2, a reductive decomposition reaction of aliquid electrolyte in a lithium battery is analyzed, and it is confirmedthat lithium methoxide and the like are formed on a surface of anelectrode. That is, in a battery environment, a liquid electrolyte willcontain lithium methoxide, which is strongly alkaline and may adverselyaffect a binder resin.

In addition, Patent Literature 3 proposes a method for producing aflexible device substrate, using a polyimide precursor resin compositionwhich comprises an organic solvent, specifically,N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, orthe like as a solvent. In the meantime, from the point of view ofenvironmental acceptability, there is a need for a compositioncomprising an aqueous solvent, as described above.

CITATION LIST Patent Literature

Patent Literature 1: JP-A-H08-59832

Patent Literature 2: JP-A-2002-226582

Patent Literature 3: JP-A-2010-202729

Non Patent Literature

Non Patent Literature 1: Technical Report of Hitachi Chemical Company,Ltd., No. 45 (July of 2005)

Non Patent Literature 2: Hiroaki YOSHIDA et al., “Decomposition Reactionof Liquid Electrolyte comprising Carbonate in Lithium Battery”, The 35thBattery Symposium Abstract Book, p. 75-76, Japan, ed. TheElectrochemical Society of Japan, The Committee of Battery Technology(Nov. 14, 1994)

SUMMARY OF INVENTION Problems to be Solved by the Invention

The first objective of the present invention is to provide an aqueouspolyimide precursor solution composition which comprises an aqueoussolvent and has good environmental acceptability, and may provide apolyimide having excellent properties such as flexibility, heatresistance, mechanical strength, electrical properties, and solventresistance, and preferably comprises a polyimide precursor (polyamicacid) having a high molecular weight and a solvent containing no organicsolvent other than water. Another objective of the present invention isto provide a method for easily producing the aqueous polyimide precursorsolution composition without the need for a solvent other than water.

The second objective of the present invention is to provide a method forproducing a polyimide seamless belt which have excellent properties suchas flexibility, heat resistance, mechanical strength, electricalproperties, and solvent resistance, and therefore may be suitably usedas an intermediate transfer seamless belt or a fixing seamless belt ofan electrophotographic device, using an aqueous polyimide precursorsolution composition which comprises an aqueous solvent and has goodenvironmental acceptability.

The third objective of the present invention is to provide a binderresin composition for electrodes which comprises an aqueous solvent andhas good environmental acceptability, and may provide a polyimide havingexcellent properties such as flexibility, heat resistance, mechanicalstrength, electrical properties, and solvent resistance, and furthermorehaving a low degree of swelling in a battery environment, and havingexcellent toughness, and preferably comprises a polyimide precursor(polyamic acid) having a high molecular weight and a solvent containingno organic solvent other than water.

The fourth objective of the present invention is to provide a polyimideprecursor resin composition for flexible device substrates whichcomprises an aqueous solvent and has good environmental acceptability,and may provide a polyimide substrate for flexible device havingexcellent properties such as flexibility, heat resistance, mechanicalstrength, electrical properties, and solvent resistance, and beingsuitably usable as a substrate for flexible device as a display devicesuch as substrates for a liquid crystal display, an organic EL displayand an electronic paper, a substrate for flexible device as alight-receiving device such as a substrate for a thin-film solar cell,and the like, and preferably comprises a polyimide precursor (polyamicacid) having a high molecular weight and a solvent containing no organicsolvent other than water.

Means for Solving the Problems

The present invention relates to the following items.

[1] An aqueous polyimide precursor solution composition, wherein apolyamic acid, which is formed by the reaction of a tetracarboxylic acidcomponent and a diamine component, and consists of a repeating unitrepresented by the following formula (1), is dissolved in an aqueoussolvent together with an imidazole in an amount of 1.6 mole or more permole of the tetracarboxylic acid component of the polyamic acid.

wherein

A represents at least one selected from the group consisting of atetravalent group of an aromatic tetracarboxylic acid containing nofluorine group, from which carboxyl groups have been removed, atetravalent group of an aliphatic tetracarboxylic acid, from whichcarboxyl groups have been removed, and a tetravalent group of anaromatic tetracarboxylic acid containing a fluorine group, from whichcarboxyl groups have been removed, and

B represents at least one selected from the group consisting of adivalent group of an aromatic diamine containing no fluorine group andhaving a solubility in water at 25° C. of 0.1 or more, from which aminogroups have been removed, a divalent group of an aliphatic diaminehaving a molecular weight of 500 or less, from which amino groups havebeen removed, and a divalent group of an aromatic diamine containing afluorine group, from which amino groups have been removed,

with the proviso that

more than 50 mol % of A is a tetravalent group of an aromatictetracarboxylic acid containing no fluorine group, from which carboxylgroups have been removed, and less than 50 mol %, including 0 mol %, ofA is a tetravalent group of an aliphatic tetracarboxylic acid, fromwhich carboxyl groups have been removed, and/or a tetravalent group ofan aromatic tetracarboxylic acid containing a fluorine group, from whichcarboxyl groups have been removed, and

more than 50 mol % of B is a divalent group of an aromatic diaminecontaining no fluorine group and having a solubility in water at 25° C.of 0.1 g/L or more, from which amino groups have been removed, and lessthan 50 mol %, including 0 mol %, of B is a divalent group of analiphatic diamine having a molecular weight of 500 or less, from whichamino groups have been removed, and/or a divalent group of an aromaticdiamine containing a fluorine group, from which amino groups have beenremoved, and

a combination of only a tetravalent group (A) of an aromatictetracarboxylic acid containing no fluorine group, from which carboxylgroups have been removed, and only a divalent group (B) of an aromaticdiamine containing no fluorine group, from which amino groups have beenremoved, is excluded.

[2] The aqueous polyimide precursor solution composition as described in[1], wherein the imidazole is selected from the group consisting of1,2-dimethylimidazole, 2-ethyl-4-methylimidazole,4-ethyl-2-methylimidazole, and 1-methyl-4-ethylimidazole.

[3] The aqueous polyimide precursor solution composition as described in[1] or [2], wherein the aqueous polyimide precursor solution compositionhas an inherent viscosity of 0.2 or more.

[4] The aqueous polyimide precursor solution composition as described inany one of [1] to [3], wherein the aqueous polyimide precursor solutioncomposition has an organic solvent content of less than 5 wt %.

[5] The aqueous polyimide precursor solution composition as described in[4], wherein the aqueous polyimide precursor solution compositioncontains substantially no organic solvent.

[6] A method for producing a polyimide seamless belt, comprising a stepof:

heating an aqueous polyimide precursor solution composition, in which apolyamic acid, which is formed by the reaction of a tetracarboxylic acidcomponent and a diamine component, and consists of a repeating unitrepresented by the following formula (1), is dissolved in an aqueoussolvent together with an imidazole in an amount of 1.6 mole or more permole of the tetracarboxylic acid component of the polyamic acid.

wherein

A represents at least one selected from the group consisting of atetravalent group of an aromatic tetracarboxylic acid containing nofluorine group, from which carboxyl groups have been removed, atetravalent group of an aliphatic tetracarboxylic acid, from whichcarboxyl groups have been removed, and a tetravalent group of anaromatic tetracarboxylic acid containing a fluorine group, from whichcarboxyl groups have been removed, and

B represents at least one selected from the group consisting of adivalent group of an aromatic diamine containing no fluorine group andhaving a solubility in water at 25° C. of 0.1 g/L or more, from whichamino groups have been removed, a divalent group of an aliphatic diaminehaving a molecular weight of 500 or less, from which amino groups havebeen removed, and a divalent group of an aromatic diamine containing afluorine group, from which amino groups have been removed,

with the proviso that

more than 50 mol % of A is a tetravalent group of an aromatictetracarboxylic acid containing no fluorine group, from which carboxylgroups have been removed, and less than 50 mol %, including 0 mol %, ofA is a tetravalent group of an aliphatic tetracarboxylic acid, fromwhich carboxyl groups have been removed, and/or a tetravalent group ofan aromatic tetracarboxylic acid containing a fluorine group, from whichcarboxyl groups have been removed, and

more than 50 mol % of B is a divalent group of an aromatic diaminecontaining no fluorine group and having a solubility in water at 25° C.of 0.1 g/L or more, from which amino groups have been removed, and lessthan 50 mol %, including 0 mol %, of B is a divalent group of analiphatic diamine having a molecular weight of 500 or less, from whichamino groups have been removed, and/or a divalent group of an aromaticdiamine containing a fluorine group, from which amino groups have beenremoved, and

a combination of only a tetravalent group (A) of an aromatictetracarboxylic acid containing no fluorine group, from which carboxylgroups have been removed, and only a divalent group (B) of an aromaticdiamine containing no fluorine group, from which amino groups have beenremoved, is excluded.

[7] A binder resin composition for electrodes, wherein

a polyamic acid, which is formed by the reaction of a tetracarboxylicacid component and a diamine component, and consists of a repeating unitrepresented by the following formula (1), is dissolved in an aqueoussolvent together with an imidazole in an amount of 1.6 mole or more permole of the tetracarboxylic acid component of the polyamic acid.

wherein

A represents at least one selected from the group consisting of atetravalent group of an aromatic tetracarboxylic acid containing nofluorine group, from which carboxyl groups have been removed, atetravalent group of an aliphatic tetracarboxylic acid, from whichcarboxyl groups have been removed, and a tetravalent group of anaromatic tetracarboxylic acid containing a fluorine group, from whichcarboxyl groups have been removed, and

B represents at least one selected from the group consisting of adivalent group of an aromatic diamine containing no fluorine group andhaving a solubility in water at 25° C. of 0.1 g/L or more, from whichamino groups have been removed, a divalent group of an aliphatic diaminehaving a molecular weight of 500 or less, from which amino groups havebeen removed, and a divalent group of an aromatic diamine containing afluorine group, from which amino groups have been removed,

with the proviso that

more than 50 mol % of A is a tetravalent group of an aromatictetracarboxylic acid containing no fluorine group, from which carboxylgroups have been removed, and less than 50 mol %, including 0 mol %, ofA is a tetravalent group of an aliphatic tetracarboxylic acid, fromwhich carboxyl groups have been removed, and/or a tetravalent group ofan aromatic tetracarboxylic acid containing a fluorine group, from whichcarboxyl groups have been removed, and

more than 50 mol % of B is a divalent group of an aromatic diaminecontaining no fluorine group and having a solubility in water at 25° C.of 0.1 g/L or more, from which amino groups have been removed, and lessthan 50 mol %, including 0 mol %, of B is a divalent group of analiphatic diamine having a molecular weight of 500 or less, from whichamino groups have been removed, and/or a divalent group of an aromaticdiamine containing a fluorine group, from which amino groups have beenremoved, and

a combination of only a tetravalent group (A) of an aromatictetracarboxylic acid containing no fluorine group, from which carboxylgroups have been removed, and only a divalent group (B) of an aromaticdiamine containing no fluorine group, from which amino groups have beenremoved, is excluded.

[8] An electrode mixture paste comprising an electrode active materialand a binder resin composition for electrodes as described in [7].

[9] An electrode produced by applying an electrode mixture paste asdescribed in [8] onto a current collector, and then heating theelectrode mixture paste to remove a solvent and effect imidization.

[10] A polyimide precursor resin composition for flexible devicesubstrates, wherein

a polyamic acid, which is formed by the reaction of a tetracarboxylicacid component and a diamine component, and consists of a repeating unitrepresented by the following formula (1), is dissolved in an aqueoussolvent together with an imidazole in an amount of 1.6 mole or more permole of the tetracarboxylic acid component of the polyamic acid.

wherein

A represents at least one selected from the group consisting of atetravalent group of an aromatic tetracarboxylic acid containing nofluorine group, from which carboxyl groups have been removed, atetravalent group of an aliphatic tetracarboxylic acid, from whichcarboxyl groups have been removed, and a tetravalent group of anaromatic tetracarboxylic acid containing a fluorine group, from whichcarboxyl groups have been removed, and

B represents at least one selected from the group consisting of adivalent group of an aromatic diamine containing no fluorine group andhaving a solubility in water at 25° C. of 0.1 g/L or more, from whichamino groups have been removed, a divalent group of an aliphatic diaminehaving a molecular weight of 500 or less, from which amino groups havebeen removed, and a divalent group of an aromatic diamine containing afluorine group, from which amino groups have been removed,

with the proviso that

more than 50 mol % of A is a tetravalent group of an aromatictetracarboxylic acid containing no fluorine group, from which carboxylgroups have been removed, and less than 50 mol %, including 0 mol %, ofA is a tetravalent group of an aliphatic tetracarboxylic acid, fromwhich carboxyl groups have been removed, and/or a tetravalent group ofan aromatic tetracarboxylic acid containing a fluorine group, from whichcarboxyl groups have been removed, and

more than 50 mol % of B is a divalent group of an aromatic diaminecontaining no fluorine group and having a solubility in water at 25° C.of 0.1 g/L or more, from which amino groups have been removed, and lessthan 50 mol %, including 0 mol %, of B is a divalent group of analiphatic diamine having a molecular weight of 500 or less, from whichamino groups have been removed, and/or a divalent group of an aromaticdiamine containing a fluorine group, from which amino groups have beenremoved, and

a combination of only a tetravalent group (A) of an aromatictetracarboxylic acid containing no fluorine group, from which carboxylgroups have been removed, and only a divalent group (B) of an aromaticdiamine containing no fluorine group, from which amino groups have beenremoved, is excluded.

[11] A method for producing a flexible device which is a display deviceor a light-receiving device, comprising steps of:

applying a polyimide precursor resin composition for flexible devicesubstrates as described in [10] onto a carrier substrate, and thenheating the composition to form a solid polyimide resin film;

forming a circuit on the polyimide resin film; and

separating the polyimide resin film on which the circuit is formed fromthe carrier substrate.

[12] A flexible device produced by a method for producing a flexibledevice as described in [11], wherein the flexible device is a displaydevice or a light-receiving device.

[13] A method for producing an aqueous polyimide precursor solutioncomposition, comprising

reacting a tetracarboxylic acid component, which comprises an aromatictetracarboxylic dianhydride containing no fluorine group in an amount ofmore than 50 mol % and comprises an aliphatic tetracarboxylicdianhydride and/or an aromatic tetracarboxylic dianhydride containing afluorine group in an amount of less than 50 mol %, or alternatively,does not comprise an aliphatic tetracarboxylic dianhydride and anaromatic tetracarboxylic dianhydride containing a fluorine group, and adiamine component, which comprises an aromatic diamine containing nofluorine group and having a solubility in water at 25° C. of 0.1 g/L ormore in an amount of more than 50 mol % and comprises an aliphaticdiamine having a molecular weight of 500 or less and/or an aromaticdiamine containing a fluorine group in an amount of less than 50 mol %,or alternatively, does not comprise an aliphatic diamine having amolecular weight of 500 or less and an aromatic diamine containing afluorine group, in the presence of an imidazole using water as areaction solvent to provide an aqueous polyimide precursor solutioncomposition,

with the proviso that

the case where a combination of an aromatic tetracarboxylic dianhydridecontaining no fluorine group and an aromatic diamine containing nofluorine group is reacted is excluded.

[14] The method for producing an aqueous polyimide precursor solutioncomposition as described in [13], wherein the amount of the imidazoleused is 1.6 mole or more per mole of the tetracarboxylic dianhydride.

Effect of the Invention

According to the present invention, there may be provided an aqueouspolyimide precursor solution composition which comprises an aqueoussolvent and has good environmental acceptability, and may provide apolyimide having excellent properties such as flexibility, heatresistance, mechanical strength, electrical properties, and solventresistance, and preferably comprises a polyimide precursor (polyamicacid) having a high molecular weight and a solvent containing no organicsolvent other than water. A polyimide having excellent properties may beobtained from the aqueous polyimide precursor solution composition,which preferably comprises a polyimide precursor (polyamic acid) havinga high molecular weight. There have been no aqueous polyimide precursorsolution compositions from which polyimides having such excellentproperties can be obtained. The flexibility of the polyimide obtained,in particular, may be improved when using an aliphatic tetracarboxylicdianhydride and/or an aliphatic diamine having a molecular weight of 500or less in addition to an aromatic tetracarboxylic dianhydride and anaromatic diamine. The flexibility of the polyimide obtained may be alsoimproved when using an aromatic tetracarboxylic dianhydride containing afluorine group (fluorine atom) and/or an aromatic diamine containing afluorine group (fluorine atom).

The polyimide which is obtained from the aqueous solution composition ofthe polyimide precursor having a specific composition and preparedaccording to the present invention, in particular, has excellentproperties such as flexibility, heat resistance, mechanical strength,electrical properties, and solvent resistance. Accordingly, thepolyimide may be suitably used as parts for various precision machinessuch as electrical/electronic equipments and a copying machine, and maybe suitably used, for example, as various materials for a flexibleprinted wiring board and the like, and as a seamless belt forintermediate transfer, fixing, or transport in a copying machine.Meanwhile, the polyimide has a low degree of swelling in a batteryenvironment, and has excellent toughness. Accordingly, the polyimide mayalso be suitably used as a binder for an electrode of a battery, and thelike. In addition, the polyimide may also be suitably used as asubstrate of a flexible device, for example, a display device such as aliquid crystal display, an organic EL display and an electronic paper,and a light-receiving device such as a light-receiving element of athin-film solar cell.

According to the present invention, there may be provided a method forproducing a polyimide seamless belt which have excellent properties suchas flexibility, heat resistance, mechanical strength, electricalproperties, and solvent resistance, and therefore may be suitably usedas an intermediate transfer seamless belt or a fixing seamless belt ofan electrophotographic device, using an aqueous polyimide precursorsolution composition which comprises an aqueous solvent and has goodenvironmental acceptability. The aqueous polyimide precursor solutioncomposition to be used preferably comprises a polyimide precursor(polyamic acid) having a high molecular weight and a solvent containingno organic solvent other than water. The method for producing apolyimide seamless belt using an aqueous polyimide precursor solutioncomposition is preferred because of having high environmentalacceptability as compared with a method wherein a polyimide precursorsolution composition in which a polyamic acid as a polyimide precursoris dissolved in an organic solvent is used. Moreover, the seamless beltof the polyimide having a specific composition which is obtainedaccording to the production method may have excellent properties such asflexibility, heat resistance, mechanical strength, electricalproperties, and solvent resistance, and therefore may be suitably usedas an intermediate transfer seamless belt or a fixing seamless belt ofan electrophotographic device, in particular, which requires highstability of electrical resistance, and high toughness.

According to the present invention, there may be also provided a binderresin composition for electrodes which comprises an aqueous solvent andhas good environmental acceptability, and may provide a polyimide havingexcellent properties such as flexibility, heat resistance, mechanicalstrength, electrical properties, and solvent resistance, and furthermorehaving a low degree of swelling in a battery environment, and havingexcellent toughness, and preferably comprises a polyimide precursor(polyamic acid) having a high molecular weight and a solvent containingno organic solvent other than water. The binder resin composition forelectrodes is preferred because of having high environmentalacceptability as compared with a polyimide precursor solutioncomposition comprising an organic solvent. Moreover, the polyimideobtained from the binder resin composition for electrodes and having aspecific composition may have excellent properties such as flexibility,heat resistance, mechanical strength, electrical properties, and solventresistance, and have a low degree of swelling in a battery environment,and have excellent toughness, and therefore may be suitably used as abinder resin composition for electrodes of electrochemical devices suchas a lithium ion secondary battery and an electric double layercapacitor.

According to the present invention, there may be also provided apolyimide precursor resin composition for flexible device substrateswhich comprises an aqueous solvent and has good environmentalacceptability, and may provide a polyimide substrate for flexible devicehaving excellent properties such as flexibility, heat resistance,mechanical strength, electrical properties, and solvent resistance, andbeing suitably usable as a substrate for flexible device as a displaydevice such as substrates for a liquid crystal display, an organic ELdisplay and an electronic paper, a substrate for flexible device as alight-receiving device such as a substrate for a thin-film solar cell,and the like, and preferably comprises a polyimide precursor (polyamicacid) having a high molecular weight and a solvent containing no organicsolvent other than water. The polyimide precursor resin composition forflexible device substrates is preferred because of having highenvironmental acceptability as compared with a polyimide precursorsolution composition comprising an organic solvent. Moreover, thepolyimide substrate for flexible device which is obtained from thepolyimide precursor resin composition and has a specific composition mayhave excellent properties such as flexibility, heat resistance,mechanical strength, electrical properties, and solvent resistance, andtherefore may be suitably used, for example, as a substrate for flexibledevice which is a display device such as substrates for a liquid crystaldisplay, an organic EL display and an electronic paper, and as asubstrate for flexible device which is a light-receiving device such asa substrate for a thin-film solar cell, in particular, which requiresflexibility, and high toughness, and may be particularly suitably usedas a substrate for a flexible display.

Moreover, according to the present invention, there may be provided amethod for easily producing an aqueous polyimide precursor solutioncomposition, which has higher environmental acceptability, without theneed for a solvent other than water. According to the production method,an aqueous polyimide precursor solution composition, particularly anaqueous polyimide precursor solution composition comprising an aqueoussolvent which has an organic solvent content of less than 5 wt %,further preferably contains no organic solvent, may be very easily(directly) produced. There have been no aqueous polyimide precursorsolution compositions having such an extremely low organic solventcontent. Now such an aqueous polyimide precursor solution compositionmay be produced by the production method of the present invention, whichallows the reaction of a tetracarboxylic acid component and a diaminecomponent in an aqueous solvent to form a polyimide precursor (polyamicacid).

DESCRIPTION OF EMBODIMENTS

According to the present invention, an aqueous polyimide precursorsolution composition is produced by reacting a tetracarboxylicdianhydride and a diamine in the presence of an imidazole, using wateras a reaction solvent, provided that

more than 50 mol % of the tetracarboxylic dianhydride to be reacted isan aromatic tetracarboxylic dianhydride containing no fluorine group,preferably an aromatic tetracarboxylic dianhydride having two to threearomatic rings and containing no fluorine group, and less than 50 mol %,including 0 mol %, of the tetracarboxylic dianhydride to be reacted isan aliphatic tetracarboxylic dianhydride and/or an aromatictetracarboxylic dianhydride containing a fluorine group, and

more than 50 mol % of the diamine to be reacted is an aromatic diaminehaving a solubility in water at 25° C. of 0.1 g/L or more and containingno fluorine group, preferably an aromatic diamine having one to twoaromatic rings, and having a solubility in water at 25° C. of 0.1 g/L ormore and containing no fluorine group, and less than 50 mol %, including0 mol %, of the diamine to be reacted is an aliphatic diamine having amolecular weight of 500 or less and/or an aromatic diamine containing afluorine group, preferably an aromatic diamine having one to twoaromatic rings, and containing a fluorine group,

with the proviso that

a combination of an aromatic tetracarboxylic dianhydride containing nofluorine group and an aromatic diamine containing no fluorine group onlyis excluded.

The term “using water as a reaction solvent” means that water is used asthe main component of the solvent. Therefore, an organic solvent otherthan water may be used in a ratio of 50 wt % or less, preferably 30 wt %or less, more preferably 10 wt % or less, relative to the whole solvent.The “organic solvent” as used herein does not include a tetracarboxylicacid component such as tetracarboxylic dianhydride, a diamine component,a polyimide precursor such as polyamic acid, and an imidazole.

Examples of the organic solvent include N,N-dimethylformamide,N,N-dimethylacetamide, N,N-diethylacetamide, N-methyl-2-pyrrolidone,N-ethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone,N-methylcaprolactam, hexamethylphosphoric triamide, 1,2-dimethoxyethane,bis(2-methoxyethy)ether, 1,2-bis(2-methoxyethoxy)ethane,tetrahydrofuran, bis [2-(2-methoxyethoxy)ethyl]ether, 1,4-dioxane,dimethyl sulfoxide, dimethyl sulfone, diphenyl ether, sulfolane,diphenyl sulfone, tetramethylurea, anisole, m-cresol, phenol, andγ-butyrolactone.

In the method for producing an aqueous polyimide precursor solutioncomposition of the present invention, the reaction solvent is preferablya solvent having an organic solvent content of less than 5 wt %,particularly preferably an aqueous solvent containing no organic solventother than water, in view of high environmental acceptability. Thecomposition of the reaction solvent may be appropriately selecteddepending on the intended solvent composition of the aqueous polyimideprecursor solution composition to be produced, and it may be preferablythe same as the intended solvent composition of the aqueous polyimideprecursor solution composition.

Preferable examples of the imidazole (compound) used in the presentinvention include a compound represented by the following formula (10).

In the formula (10), X₁ to X₄ each independently represents a hydrogenatom or an alkyl group having 1 to 5 carbon atoms.

The imidazole used in the present invention preferably has a solubilityin water at 25° C. of 0.1 g/L or more, particularly preferably 1 g/L ormore.

In the imidazole of the formula (10), X₁ to X₄ each independentlyrepresents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.An imidazole in which at least two of X₁ to X₄ are alkyl groups having 1to 5 carbon atoms, or an imidazole having two or more alkyl groups assubstituents is more preferred.

An imidazole having two or more alkyl groups as substituents has highsolubility in water, and therefore, when using such an imidazole, anaqueous polyimide precursor solution composition may be easily produced.Preferable examples of the imidazole include 1,2-dimethylimidazole(solubility in water at 25° C.: 239 g/L; the same shall applyhereinafter), 2-ethyl-4-methylimidazole (1000 g/L),4-ethyl-2-methylimidazole (1000 g/L), and 1-methyl-4-ethylimidazole (54g/L).

The “solubility in water at 25° C.” means the maximum amount (g) of thesubstance soluble in 1 L (liter) of water at 25° C. This value may beeasily searched using SciFinder®, which is known as a search servicebased on the data bases such as Chemical Abstracts. Among the variousvalues of solubility under various conditions, the values at pH 7, whichare calculated by Advanced Chemistry Development (ACD/Labs) SoftwareV11.02 (Copyright 1994-2011 ACD/Labs), are used herein.

The imidazole to be used may be a single imidazole, or may be a mixtureof two or more imidazoles.

The amount of the imidazole used in the present invention is preferably0.8 equivalents or more, more preferably 1.0 equivalent or more, furtherpreferably 1.2 equivalents or more per equivalent of the carboxyl groupof the polyamic acid, which is formed by the reaction of atetracarboxylic dianhydride and a diamine as starting materials. Whenthe amount of the imidazole used is less than 0.8 equivalents perequivalent of the carboxyl group of the polyamic acid, it may not beeasy to provide an aqueous polyimide precursor solution composition inwhich the polyamic acid is homogeneously dissolved. In addition, theupper limit of the amount of the imidazole used may be generally, butnot limited to, less than 10 equivalents, preferably less than 5equivalents, more preferably less than 3 equivalents per equivalent ofthe carboxyl group of the polyamic acid. If the amount of the imidazoleused is too great, it will be uneconomical, and the storage stability ofthe aqueous polyimide precursor solution composition may be reduced.

In the present invention, the “equivalents per equivalent of thecarboxyl group of the polyamic acid”, which defines the amount of theimidazole, means the number (number of molecules) of imidazole used perone carboxyl group to form an amic acid group in the polyamic acid. Thenumber of carboxyl groups to form amic acid groups in the polyamic acidsmay be calculated on the assumption that two carboxyl groups would beformed per one molecule of the tetracarboxylic acid component as astarting material.

Accordingly, the amount of the imidazole used in the present inventionis preferably 1.6 mole or more, more preferably 2.0 mole or more,further preferably 2.4 mole or more per mole of the tetracarboxylicdianhydride as a starting material (per mole of the tetracarboxylic acidcomponent of the polyamic acid).

The characteristics of the imidazole used in the present invention arethat the imidazole forms a salt with a carboxyl group of a polyamic acid(polyimide precursor), which is formed by the reaction of atetracarboxylic dianhydride and a diamine as starting materials, therebyincreasing the solubility of the polyamic acid in water, and also thatthe imidazole exhibits a very high catalytic activity during theimidization (dehydration/ring closure) of the polyimide precursor toform a polyimide Consequently, when using the aqueous polyimideprecursor solution composition of the present invention, a polyimide, apolyimide seamless belt, a binder resin for electrodes, and a substratefor flexible devices, which have very high properties, may be easilyproduced even though the aqueous polyimide precursor solutioncomposition is heated at a lower temperature for a shorter period oftime, for example.

As described above, according to the present invention, an aqueouspolyimide precursor solution composition may be very easily (directly)produced preferably by reacting a tetracarboxylic acid component and adiamine component in the presence of an imidazole, preferably in thepresence of an imidazole having two or more alkyl groups assubstituents, using water as a reaction solvent.

The reaction is performed at a relatively low temperature of 100° C. orlower, preferably 80° C. or lower, so as to suppress the imidizationreaction, using substantially equimolar amounts of a tetracarboxylicacid component (tetracarboxylic dianhydride) and a diamine component.The reaction temperature may be generally, but not limited to, from 25°C. to 100° C., preferably from 40° C. to 80° C., more preferably from50° C. to 80° C. The reaction time may be preferably, but not limitedto, from about 0.1 hours to about 24 hours, preferably from about 2hours to about 12 hours. When setting the reaction temperature and thereaction time within the ranges as described above, an aqueous polyimideprecursor solution composition which comprises a polyimide precursorhaving a high molecular weight may be easily produced with goodproduction efficiency. In general, the reaction may be preferablyperformed in an inert gas atmosphere, preferably in a nitrogen gasatmosphere, although the reaction may be performed in an air atmosphere.

In addition, the “substantially equimolar amounts of a tetracarboxylicacid component (tetracarboxylic dianhydride) and a diamine component”specifically means that a molar ratio [tetracarboxylic acidcomponent/diamine component] is from about 0.90 to about 1.10,preferably from about 0.95 to about 1.05.

The tetracarboxylic dianhydride used in the present invention is anaromatic tetracarboxylic dianhydride containing no fluorine group andpreferably having two to three aromatic rings, or alternatively, anaromatic tetracarboxylic dianhydride containing no fluorine group andpreferably having two to three aromatic rings, and an aliphatictetracarboxylic dianhydride and/or an aromatic tetracarboxylicdianhydride containing a fluorine group, and may be more preferably, butnot limited to, a combination of an aromatic tetracarboxylic dianhydridecontaining no fluorine group and an alicyclic tetracarboxylicdianhydride, in terms of the properties of the polyimide obtained. Whenthe diamine component to be reacted is only an aromatic diaminecontaining no fluorine group, however, both an aromatic tetracarboxylicdianhydride containing no fluorine group, and an aliphatictetracarboxylic dianhydride and/or an aromatic tetracarboxylicdianhydride containing a fluorine group are used.

Preferable examples of the aromatic tetracarboxylic dianhydridecontaining no fluorine group used in the present invention include3,3′,4,4′-biphenyltetracarboxylic dianhydride,2,3,3′,4′-biphenyltetracarboxylic dianhydride,2,2′,3,3′-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride,benzophenone tetracarboxylic dianhydride, 4,4′-oxydiphthalicdianhydride, diphenylsulfone tetracarboxylic dianhydride, p-terphenyltetracarboxylic dianhydride, and m-terphenyl tetracarboxylicdianhydride.

Preferable examples of the aliphatic tetracarboxylic dianhydride used inthe present invention include cyclobutane-1,2,3,4-tetracarboxylicdianhydride, 1,2,4,5-cyclohexane tetracarboxylic dianhydride,dicyclohexyl-3,3′,4,4′-tetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic acid-1,2:4,5-dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, andbicyclo[2.2.2]octo-7-ene-2,3;5,6-tetracarboxylic dianhydride.

Preferable examples of the aromatic tetracarboxylic dianhydridecontaining a fluorine group used in the present invention include4,4′-(hexafluoroisopropylidene)diphthalic anhydride,3,3′-(hexafluoroisopropylidene)diphthalic anhydride,5,5′-[2,2,2-trifluoro-1-[3-(trifluoromethyl)phenyl]ethylidene]diphthalicanhydride, 5,5′-anhydride,1H-diflo[3,4-b:3′,4′-i]xanthene-1,3,7,9(11H)-tetron,5,5′-oxybis[4,6,7-trifluoro-pyromellitic anhydride],3,6-bis(trifluoromethyl)pyromellitic dianhydride,4-(trifluoromethyl)pyromellitic dianhydride, 1, 4-difluoropyromelliticdianhydride, and 1,4-bis(3,4-dicarboxytrifluorophenoxy)tetrafluorobenzene dianhydride.

The aromatic tetracarboxylic dianhydride containing no fluorine group,the aliphatic tetracarboxylic dianhydride, and the aromatictetracarboxylic dianhydride containing a fluorine group each may not bea single component, and may be a mixture of two or more types thereof.

The diamine used in the present invention is an aromatic diamine havinga solubility in water at 25° C. of 0.1 g/L or more and containing nofluorine group and preferably having one to two aromatic rings, oralternatively, an aromatic diamine having a solubility in water at 25°C. of 0.1 g/L or more and containing no fluorine group and preferablyhaving one to two aromatic rings, and an aliphatic diamine having amolecular weight of 500 or less and/or an aromatic diamine containing afluorine group. When the tetracarboxylic acid component to be reacted isonly an aromatic tetracarboxylic dianhydride containing no fluorinegroup, however, both an aromatic diamine containing no fluorine group,and an aliphatic diamine and/or an aromatic diamine containing afluorine group are used.

The aromatic diamine containing no fluorine group used in the presentinvention is not limited as long as the solubility in water at 25° C. is0.1 g/L or more, but may be preferably an aromatic diamine having one totwo aromatic rings. When an aromatic diamine having a solubility inwater at 25° C. of less than 0.1 g/L is used, it may be difficult toprovide an aqueous polyimide precursor solution composition in which thepolyimide precursor is homogeneously dissolved. Meanwhile, when thearomatic diamine has more than two aromatic rings, the aromatic diaminemay have a solubility in water at 25° C. of less than 0.1 g/L, andtherefore it may be difficult to provide an aqueous polyimide precursorsolution composition in which the polyimide precursor is homogeneouslydissolved.

The aliphatic diamine used in the present invention is not limited aslong as the molecular weight (which means “molecular weight” in the caseof monomer, and “weight average molecular weight” in the case ofpolymer) is 500 or less, but may be preferably an aliphatic diaminehaving a solubility in water at 25° C. of 0.1 g/L or more, or analicyclic diamine having one to two alicyclic rings. When an aliphaticdiamine having a molecular weight of more than 500 is used, it may bedifficult to provide an aqueous polyimide precursor solution compositionin which the polyimide precursor is homogeneously dissolved.

The aromatic diamine containing a fluorine group used in the presentinvention may be preferably, but not limited to, an aromatic diaminehaving one to two aromatic rings and containing a fluorine group. Whenthe aromatic diamine containing a fluorine group has more than twoaromatic rings, it may be difficult to provide an aqueous polyimideprecursor solution composition in which the polyimide precursor ishomogeneously dissolved.

Preferable examples of the aromatic diamine containing no fluorine groupused in the present invention include p-phenylenediamine (solubility inwater at 25° C.: 120 g/L; the same shall apply hereinafter),m-phenylenediamine (77 g/L), 4,4′-diaminodiphenyl ether (0.19 g/L),3,4′-diaminodiphenyl ether (0.24 g/L), 4,4′-diaminodiphenylmethane (0.54g/L), 2,4-toluenediamine (62 g/L), 3,3′-dihydroxy-4,4′-diaminobiphenyl(1.3 g/L), bis(4-amino-3-carboxyphenyl)methane (200 g/L), and2,4-diaminotoluene (62 g/L). Among them, in terms of the high solubilityin water, and excellent properties of the polyimide obtained,p-phenylenediamine, m-phenylenediamine, 4,4′-diaminodiphenyl ether,3,4′-diaminodiphenyl ether, and a mixture thereof are preferred, andp-phenylenediamine, 4,4′-diaminodiphenyl ether, and a mixture thereofare more preferred.

Preferable examples of the aliphatic diamine used in the presentinvention include trans-1,4-diaminocyclohexane (1000 g/L, molecularweight: 114), cis-1,4-diaminocyclohexane (1000 g/L, molecular weight:114), 1,6-hexamethylene diamine (1000 g/L, molecular weight: 116),1,10-decamethylene diamine (1000 g/L, molecular weight: 172),1,3-bis(aminomethyl)cyclohexane (1000 g/L, molecular weight: 142),1,4-bis(aminomethyl)cyclohexane (999 g/L, molecular weight: 142), andpolyoxypropylene diamine having a weight average molecular weight of 500or less.

Preferable examples of the aromatic diamine containing a fluorine groupused in the present invention include2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl,2,3,5,6-tetrafluoro-1,4-diaminobenzene,2,4,5,6-tetrafluoro-1,3-diaminobenzene,2,3,5,6-tetrafluoro-1,4-benzene(dimethaneamine),2,2′-difluoro-(1,1′-biphenyl)-4,4′-diamine,2,2′,6,6′-tetrafluoro-(1,1′-biphenyl)-4,4′-diamine, 4,4′-diaminooctafluorobiphenyl, 2,2-bis(4-aminophenyl) hexafluoropropane, and4,4′-oxybis(2,3,5,6-tetrafluoroaniline).

The aromatic diamine containing no fluorine group, the aliphaticdiamine, and the aromatic diamine containing a fluorine group each maynot be a single component, and may be a mixture of two or more typesthereof. As for the aromatic diamine containing no fluorine group, it isalso possible to use a diamine which has a high solubility in water incombination with other diamines such that the diamine component has asolubility in water at 25° C. of 0.1 g/L or more as a whole.

The “diamine having a solubility in water at 25° C. of 0.1 g/L or more”means that 0.1 g or more of the diamine is dissolved in 1 L (1000 ml) ofwater at 25° C. The “solubility in water at 25° C.” means the maximumamount (g) of the substance soluble in 1 L (liter) of water at 25° C.This value may be easily searched using SciFinder®, which is known as asearch service based on the data bases such as Chemical Abstracts. Amongthe various values of solubility under various conditions, the values atpH 7, which are calculated by Advanced Chemistry Development (ACD/Labs)Software V11.02 (Copyright 1994-2011 ACD/Labs), are used herein.

In the present invention, it is preferred that

-   (I) a tetracarboxylic acid component consisting of one or more    aromatic tetracarboxylic dianhydrides containing no fluorine group,    and one or more aliphatic tetracarboxylic dianhydrides and/or one or    more aromatic tetracarboxylic dianhydrides containing a fluorine    group, and a diamine component consisting of one or more aromatic    diamines containing no fluorine group are reacted, or-   (II) a tetracarboxylic acid component consisting of one or more    aromatic tetracarboxylic dianhydrides containing no fluorine group,    and a diamine component consisting of one or more aromatic diamines    containing no fluorine group, and one or more aliphatic diamines    and/or one or more aromatic diamines containing a fluorine group are    reacted.    In the case of (I), the amount of the aromatic tetracarboxylic    dianhydride containing no fluorine group in the tetracarboxylic acid    component is not limited as long as the amount is more than 50 mol    %, but may be preferably more than 50 mol % and not more than 80 mol    % in terms of the properties of the polyimide obtained. In the case    of (II), the amount of the aromatic diamine having a solubility in    water at 25° C. of 0.1 g/L or more and containing no fluorine group    in the diamine component is not limited as long as the amount is    more than 50 mol %, but may be preferably not less than 60 mol % and    not more than 90 mol % in terms of the properties of the polyimide    obtained.

The polyamic acid which constitutes the aqueous polyimide precursorsolution composition of the present invention consists of a repeatingunit represented by the formula (1).

In the formula (1), the “A” group is a chemical structure derived fromthe tetracarboxylic acid component of a polyamic acid, and is atetravalent group of an aromatic tetracarboxylic acid containing nofluorine group and preferably having two to three aromatic rings, fromwhich carboxyl groups have been removed, and/or a tetravalent group ofan aliphatic tetracarboxylic acid, from which carboxyl groups have beenremoved, and/or a tetravalent group of an aromatic tetracarboxylic acidcontaining a fluorine group, from which carboxyl groups have beenremoved.

As for the “A” group in the formula (1), more than 50 mol % of A ispreferably a tetravalent, group of an aromatic tetracarboxylic acidcontaining no fluorine group and preferably having two to three aromaticrings, from which carboxyl groups have been removed, and less than 50mol % of A is preferably a tetravalent group of an aliphatictetracarboxylic acid, from which carboxyl groups have been removed,and/or a tetravalent group of an aromatic tetracarboxylic acidcontaining a fluorine group, from which carboxyl groups have beenremoved, so as to provide a polyamic acid having an adequate solubilityin water, and to provide a polyimide having excellent flexibility, heatresistance, mechanical strength, electrical properties and solventresistance, thereby easily producing a polyimide seamless belt, a binderresin for electrodes, and a polyimide substrate for flexible devices,which have high properties.

In the present invention, in terms of the properties of the polyimideobtained, the “A” group in the formula (1) which is a constituent unitderived from the aromatic tetracarboxylic dianhydride containing nofluorine group is preferably any one or more of the groups representedby the following formulas (2) to (7), particularly preferably any one ormore of the groups represented by the following formulas (2), (3) and(5) in the main, further preferably any one or more of the groupsrepresented by the following formulas (2) to (3).

In the formula (1), the “B” group is a chemical structure derived fromthe diamine component of a polyamic acid, and is a divalent group of anaromatic diamine having a solubility in water at 25° C. of 0.1 g/L ormore and containing no fluorine group and preferably having one to twoaromatic rings, from which amino groups have been removed, anchor adivalent group of an aliphatic diamine having a molecular weight of 500or less, preferably an aliphatic diamine having a solubility in water of0.1 g/L or more, or an aliphatic diamine having one to two alicyclicrings, from which amino groups have been removed, and/or a divalentgroup of an aromatic diamine containing a fluorine group, preferably anaromatic diamine containing a fluorine group and having one to twoaromatic rings, from which amino groups have been removed.

As for the “B” group in the formula (1), more than 50 mol % of B ispreferably a divalent group of an aromatic diamine having a solubilityin water at 25° C. of 0.1 g/L or more and containing no fluorine groupand preferably having one to two aromatic rings, from which amino groupshave been removed, and less than 50 mol % of B is preferably a divalentgroup of an aliphatic diamine having a molecular weight of 500 or less,from which amino groups have been removed, and/or a divalent group of anaromatic diamine containing a fluorine group, from which amino groupshave been removed, so as to provide a polyamic acid having an adequatesolubility in water, and to provide a polyimide having excellentflexibility, heat resistance, mechanical strength, electrical propertiesand solvent resistance, thereby easily producing a polyimide seamlessbelt, a binder resin for electrodes, and a polyimide substrate forflexible devices, which have high properties.

In the present invention, in terms of the properties of the polyimideobtained, the “B” group in the formula (1) which is a constituent unitderived from the aromatic diamine containing no fluorine group ispreferably any one or more of the groups represented by the followingformulas (8) to (9).

In the aqueous polyimide precursor solution composition obtainedaccording to the present invention, the polyimide precursor (which issubstantially a polyamic acid) preferably has a high molecular weight,and more specifically, has an inherent viscosity of 0.2 or more,preferably 0.4 or more, more preferably 0.6 or more, further preferably0.8 or more, particularly preferably 1.0 or more, or more than 1.0,wherein the inherent viscosity is measured at a temperature of 30° C.and a concentration of 0.5 g/100 mL (dissolved in water) which is basedon the solid content of the polyimide precursor. When the inherentviscosity is lower than the range as described above, the polyimideprecursor has a low molecular weight, and therefore it may be difficultto provide a polyimide, a polyimide seamless belt, a binder resin forelectrodes, and a polyimide substrate for flexible devices, which havehigh properties, even if the aqueous polyimide precursor solutioncomposition of the present invention is used.

The solid content based on the polyimide precursor (which issubstantially a polyamic acid) of the aqueous polyimide precursorsolution composition of the present invention may be preferably, but notlimited to, from 5 wt % to 45 wt %, more preferably from 7 wt % to 40 wt%, further preferably from 9 wt % to 30 wt %, relative to the totalamount of the polyimide precursor and the solvent. When the solidcontent is lower than 5 wt %, the productivity and the handling in usemay be reduced. When the solid content is higher than 45 wt %, thesolution may lose the fluidity.

In view of handling properties, the solution viscosity at 30° C. of theaqueous polyimide precursor solution composition of the presentinvention may be preferably, but not limited to, 1000 Pa·sec or lower,more preferably from 0.5 Pa·sec to 500 Pa·sec, further preferably from 1Pa·sec to 300 Pa·sec, particularly preferably from 3 Pa·sec to 200Pa·sec. When the solution viscosity is higher than 1000 Pa·sec, thecomposition may lose the fluidity, and therefore it may be difficult touniformly apply the composition onto a metal (such as a currentcollecting foil), a glass, and the like. When the solution viscosity islower than 0.5 Pa·sec, dripping, cissing, and the like may occur whenapplying the composition onto a metal (such as a current collectingfoil), a glass, and the like, and it may be difficult to provide apolyimide, a polyimide seamless belt, a binder resin for electrodes, anda polyimide substrate for flexible devices, which have high properties.

Although the aqueous polyimide precursor solution composition of thepresent invention comprises an aqueous solvent, an organic solvent otherthan water, for example, a known organic solvent to be used in thepreparation of a polyamic acid may be used in a ratio of 50 wt % orless, preferably 30 wt % or less, more preferably 10 wt % or less,relative to the whole solvent. In other words, the aqueous polyimideprecursor solution composition of the present invention is a compositionin which a polyamic acid as a polyimide precursor is dissolved, togetherwith an imidazole, in an aqueous solvent (water-based solvent), whereinthe aqueous solvent is only water, or a mixture of water and an organicsolvent having a water content of 50 wt % or more, preferably 70 wt % ormore, more preferably 90 wt % or more.

Examples of the organic solvent include N,N-dimethylformamide,N,N-dimethylacetamide, N,N-diethylacetamide, N-methyl-2-pyrrolidone,N-ethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone,N-methylcaprolactam, hexamethylphosphoric triamide, 1,2-dimethoxyethane,bis(2-methoxyethyl)ether, 1,2-bis(2-methoxyethoxy)ethane,tetrahydrofuran, bis[2-(2-methoxyethoxy)ethyl]ether, 1,4-dioxane,dimethyl sulfoxide, dimethyl sulfone, diphenyl ether, sulfolane,diphenyl sulfone, tetramethylurea, anisole, m-cresol, phenol, andγ-butyrolactone.

In the aqueous polyimide precursor solution composition of the presentinvention, the solvent is particularly preferably a solvent having anorganic solvent content of less than 5 wt %, more preferably an aqueoussolvent containing no organic solvent other than water, i.e. only water,in view of environmental acceptability.

The aqueous polyimide precursor solution composition of the presentinvention may also be prepared according to the following methods, forexample, as described in Patent Literatures 1 and 2:

(i) a method, comprising

-   -   pouring a polyamide acid, which is prepared by reacting a        tetracarboxylic acid component with a diamine component in an        organic solvent as a reaction solvent, into water to provide a        polyamide acid powder; and    -   mixing and dissolving the polyamide acid powder, together with        an imidazole (preferably, an imidazole having two or more alkyl        groups), into an aqueous solvent to provide an aqueous solution        composition;

(ii) a method, comprising

-   -   reacting a tetracarboxylic acid component with a diamine        component in an organic solvent as a reaction solvent in the        presence of an imidazole (preferably, an imidazole having two or        more alkyl groups) to provide a water-soluble polyimide        precursor;    -   separating the water-soluble polyimide precursor therefrom; and    -   dissolving the separated water-soluble polyimide precursor in an        aqueous solvent; and

(iii) a method, comprising

-   -   reacting a tetracarboxylic acid component with a diamine        component in an organic solvent as a reaction solvent to provide        a polyamic acid;    -   reacting the polyamic acid with an imidazole (preferably, an        imidazole having two or more alkyl groups) in an organic solvent        as a reaction solvent to provide a water-soluble polyimide        precursor;    -   separating the water-soluble polyimide precursor therefrom; and    -   dissolving the separated water-soluble polyimide precursor in an        aqueous solvent.        As described above, however, in order to obtain an aqueous        polyimide precursor solution composition having an extremely low        organic solvent content, or containing no organic solvent, it is        not preferred that a polyimide precursor is prepared in an        organic solvent.

Generally, a polyimide may be suitably prepared by heating the aqueouspolyimide precursor solution composition of the present invention toremove an aqueous solvent and effect imidization (dehydration/ringclosure). The heat treatment conditions are not limited, but, ingeneral, the aqueous polyimide precursor solution composition may bepreferably heated at a temperature of 100° C. or higher, preferably from120° C. to 600° C., more preferably from 150° C. to 500° C., furtherpreferably from 150° C. to 350° C., for from 0.01 hours to 30 hours,preferably from 0.01 hours to 10 hours, preferably while increasing thetemperature stepwise.

The heat treatment may be suitably performed under atmospheric pressure,and may be performed under reduced pressure so as to efficiently removethe aqueous solvent. The aqueous polyimide precursor solutioncomposition may be heated at a relatively low temperature under reducedpressure at the early stage for deaeration. When the heating temperatureis rapidly increased, a problem such as foaming may occur.

The aqueous polyimide precursor solution composition of the presentinvention may be heated at a relatively low temperature (for example,150° C. to 300° C., preferably 180° C. to 250° C.) to readily provide apolyimide, which has excellent properties, for example, highadhesiveness to a metal and the like, and is in no way inferior to apolyimide obtained from a commonly-used polyimide precursor (polyamicacid) solution composition comprising an organic solvent. Accordingly, apolyimide seamless belt and the like, as well as a polyimide film, maybe suitably obtained from the aqueous polyimide precursor solutioncomposition of the present invention.

According to the method for producing the polyimide seamless belt of thepresent invention, a coating film of an aqueous polyimide precursorsolution composition layer is formed on a substrate by applying orspraying an aqueous polyimide precursor solution composition(specifically, an aqueous polyimide precursor solution composition inwhich a polyamic acid consisting of a repeating unit represented by theformula (1) is homogeneously dissolved in an aqueous solvent togetherwith an imidazole in an amount of 1.6 mole or more per mole of thetetracarboxylic acid component of the polyamic acid) onto the substratesurface, and then the aqueous polyimide precursor solution compositionis heated.

According to the present invention, a polyimide seamless belt may besuitably prepared by heating the aqueous polyimide precursor solutioncomposition to remove an aqueous solvent and effect imidization(dehydration/ring closure). The heat treatment conditions are notlimited, but, in general, the aqueous polyimide precursor solutioncomposition may be preferably heated at a temperature of 100° C. orhigher, preferably from 120° C. to 600° C., more preferably from 150° C.to 500° C., further preferably from 150° C. to 350° C., for from 0.01hours to 30 hours, preferably from 0.01 hours to 10 hours, preferablywhile increasing the temperature stepwise.

The heat treatment may be suitably performed under atmospheric pressure,and may be performed under reduced pressure so as to efficiently removethe aqueous solvent. The aqueous polyimide precursor solutioncomposition may be heated at a relatively low temperature under reducedpressure at the early stage for deaeration. When the heating temperatureis rapidly increased, a problem such as foaming may occur, and thereforea polyimide seamless belt having excellent properties may not beobtained.

According to the method for producing the polyimide seamless belt of thepresent invention, the aqueous polyimide precursor solution compositionmay be heated at a relatively low temperature. (for example, 150° C. to300° C., preferably 180° C. to 250° C.) to readily provide a polyimideseamless belt, which has excellent properties, and is in no way inferiorto a polyimide seamless belt obtained from a commonly-used polyimideprecursor (polyamic acid) solution composition comprising an organicsolvent.

Any known method for forming a seamless belt may be suitably employed.For example, a seamless belt may be suitably produced by rotationalmolding, i.e. a method comprising

forming a coating film of an aqueous polyimide precursor solutioncomposition by application (coating) or spraying, for example, on asurface (inner surface or outer surface) of a cylindrical mold, whichfunctions as a substrate, while rotating the mold;

heating the coating film at a relatively low temperature to effect theremoval of the aqueous solvent, thereby forming a self-supporting film(the film in a state of not flowing; the polymerization and partialimidization reaction, as well as the removal of the aqueous solvent,proceed.); and

heating the self-supporting film on the substrate, or alternatively, theself-supporting film which is peeled from the substrate, if necessary,to effect dehydration/imidization.

The terms “removal of the aqueous solvent” and “dehydration/imidization”as used herein do not mean that only the removal of the aqueous solventproceeds and only the dehydration/imidization proceeds, respectively, inthe steps. In the aqueous solvent removal step, thedehydration/imidization proceeds to some extent. In thedehydration/imidization step, the removal of the residual aqueoussolvent proceeds.

The aqueous polyimide precursor solution composition of the presentinvention may contain other additive component(s) depending on theintended application of the polyimide seamless belt obtained.Additionally, another resin layer and/or a metal layer may be laminatedon the polyimide seamless belt obtained.

The thickness of the polyimide seamless belt of the present inventionmay be appropriately selected depending on the intended use, and it maybe generally from about 20 μm to about 200 μm.

The polyimide seamless belt obtained according to the present inventionpreferably has excellent properties such as flexibility, heatresistance, mechanical strength, electrical properties, and solventresistance, and therefore it may be suitably used as an intermediatetransfer seamless belt or a fixing seamless belt of anelectrophotographic device.

When the polyimide seamless belt is used as an intermediate transferbelt of an electrophotographic device, a conductive filler may bepreferably added to the seamless belt so that semiconductivity isimparted to the seamless belt, specifically, the seamless belt has asurface resistivity of 10⁸ Ω/□ to 10¹⁶ Ω/□ and a volume resistivity of10⁸ Ω·cm to 10¹⁶ Ω·cm.

A conductive or semiconductive particle which is used for a conventionalintermediate transfer seamless belt may be used as the conductivefiller. Examples thereof include, but not limited to, carbon blacks suchas ketjen black and acetylene black, metals such as aluminum and nickel,metal oxide compounds such as tin oxide, and potassium titanate. Theconductive filler may be used alone or in combination of two or more. Inthe present invention, a carbon black may be preferably used as theconductive filler, and, among them, a carbon black having an averageprimary particle size of from 5 nm to 100 nm, particularly preferablyfrom 10 nm to 50 nm, is particularly preferred. When the average primaryparticle size is more than 100 nm, the uniformity of mechanicalproperties and electric resistance may be liable to be inadequate.

The amount of the conductive filler may vary depending on the type,particle size, and a dispersion state of the filler. In general, theamount of the conductive filler is preferably from 1 to 50 parts byweight, more preferably from 2 to 30 parts by weight, relative to 100parts by weight of the polyimide (solid content). In the presentinvention, the surface resistivity and the volume resistivity may becontrolled to within the range (10⁸ Ω/□ to 10¹⁶ Ω/□, and 10⁸ Ω·cm to10¹⁶ Ω·cm) suitable for an intermediate transfer belt by a combinationof the selection of the conductive filler and its appropriate amount.

When the polyimide seamless belt is used as a fixing belt of anelectrophotographic device, a filler such as silica, boron nitride,aluminum nitride, silicon nitride, and alumina may be preferably addedto the seamless belt so that thermal conductivity is imparted to theseamless belt, and a fluororesin powder, for example, may be preferablyadded to the seamless belt so that rubber elasticity is imparted to theseamless belt, and a metal foil as a heating element may be preferablylaminated on the seamless belt. In general, the amount of the filler ispreferably from 1 to 50 parts by weight, more preferably from 2 to 30parts by weight, relative to 100 parts by weight of the polyimide (solidcontent).

When the polyimide seamless belt is used as a fixing belt of anelectrophotographic device, the seamless belt may preferably have athermal conductivity of 0.15 W/mK or more, preferably 0.20 W/mK or more.

In addition, when the polyimide seamless belt is used as a fixing beltof an electrophotographic device, the seamless belt may preferably havea rubber elastic layer or a release layer laminated on the surface. Therelease layer (parting layer) is not limited as long as the layerimproves the releasability of the surface of the seamless belt, and aknown material including polytetrafluoroethylene (PTFE), and a modifiedmaterial thereof such as tetrafluoroethylene-perfluoroalkylvinylethercopolymer (PFA), tetrafluoroethylene-ethylene copolymer (ETFE),tetrafluoroethylene-hexafluoropropylene copolymer (FEP),tetrafluoroethylene-vinylidene fluoride copolymer (TFE/VdF),tetrafluoroethylene-hexafluoropropylene-perfluoroalkylvinylethercopolymer (EPA), polychlorotrifluoroethylene (PCTFE),chlorotrifluoroethylene-ethylene copolymer (ECTFE),chlorotrifluoroethylene-vinylidene fluoride copolymer (CTFE/VdF),polyvinylidene fluoride (PVdF), and polyvinyl fluoride (PVF) may besuitably used for the release layer. The rubber elastic layer may alsobe formed of the material as described above. The surface layer maypreferably contain a conductive filler.

The aqueous polyimide precursor solution composition of the presentinvention may also be suitably used as a binder resin composition forelectrodes.

Generally, a polyimide may be suitably prepared by heating the aqueouspolyimide precursor solution composition of the present invention(binder resin composition for electrodes of the present invention) toremove an aqueous solvent and effect imidization (dehydration/ringclosure) in this case, as well. The heat treatment conditions are notlimited, but, in general, the aqueous polyimide precursor solutioncomposition may be preferably heated at a temperature of 100° C. orhigher, preferably from 120° C. to 600° C., more preferably from 150° C.to 500° C., for from 0.01 hours to 30 hours, preferably from 0.01 hoursto 10 hours.

As for the properties of the polyirnide obtained from the binder resincomposition for electrodes of the present invention, the binder resincomposition for electrodes may be heated at a relatively low temperature(for example, 150° C. to 300° C., preferably 180° C. to 250° C.) toprovide a polyimide, which has excellent properties, for example, highadhesiveness to a metal, and is in no way inferior to a polyimideobtained from a commonly-used binder resin composition for electrodescomprising an organic solvent.

The binder resin composition for electrodes of the present invention maybe suitably used as a binder resin composition for batteries, becausethe polyimide resin, which is obtained by the heat treatment asdescribed above, preferably has a weight increase of 3 wt % or less,more preferably 2 wt % or less, further preferably 1 wt % or less, whenimmersed in dimethyl carbonate for 24 hours at a temperature of 25° C.Here dimethyl carbonate is a compound commonly used as an electrolytecomponent of a battery, and when the weight increase in a liquidelectrolyte (rate of swelling when immersed in the liquid electrolytefor 24 hours at a temperature of 25° C.) of the binder resin, which iscaused by swelling by the liquid electrolyte, is 5 wt % or less, morepreferably 3 wt % or less, particularly preferably 2 wt % or less, theinfluence of the volume change of the electrode may be suitably reduced.

In addition, lithium methoxide is often formed in a battery environment.The polyimide resin obtained from the binder resin composition forelectrodes of the present invention preferably has a weight increase ina liquid electrolyte containing lithium methoxide (rate of swelling whenimmersed in the liquid electrolyte for 24 hours at a temperature of 25°C.) of 5 wt % or less, more preferably 3 wt % or less, particularlypreferably 2 wt % or less.

An electrode mixture paste may be suitably prepared by mixing the binderresin composition for electrodes of the present invention with at leastan electrode active material, preferably, but not limited to, at atemperature of from 10° C. to 60° C. Any known electrode active materialmay be suitably used, and a lithium-containing metal composite oxide, acarbon powder, a silicon powder, a tin powder, and a silicon-containingor tin-containing alloy powder may be more preferred. The amount of theelectrode active material in the electrode mixture paste may begenerally, but not limited to, from 0.1 to 1000 times, preferably from 1to 1000 times, more preferably from 5 to 1000 times, further preferablyfrom 10 to 1000 times, the weight of the solid content based on thepolyamic acid on a weight basis. When the amount of the electrode activematerial is too small, the greater part of the active material layerformed on a current collector may be inactive, resulting in theinadequate function of the electrode. When the amount of the electrodeactive material is too large, the electrode active material may not befirmly bound to a current collector and may be readily detached. Inaddition, the electrode mixture paste may contain an additive such as asurfactant, a viscosity modifier, and a conductive auxiliary agent, asnecessary. The solid content of the polyamic acid may be preferably from1 wt % to 15 wt %, relative to the whole solid content in the electrodemixture paste. When the solid content of the polyamic acid is outsidethe above-mentioned range, the performance of the electrode may bedegraded.

An electrode may be produced by

flow-casting or applying an electrode mixture paste onto a conductivecurrent collector such as aluminum, wherein the electrode mixture pastecomprises the binder resin composition for electrodes of the presentinvention, and an electrode active material which is capable ofreversibly incorporating and releasing lithium ion on charge anddischarge, for example, a lithium-containing metal composite oxide; andthen

heating the electrode mixture paste at a temperature of from 80° C. to400° C., more preferably from 120° C. to 300° C., particularlypreferably from 150° C. to 250° C., to remove a solvent and effectimidization.

When the heating temperature is outside the above-mentioned range, theimidization reaction may not sufficiently proceed, and the properties ofthe formed electrode may be degraded. The heat treatment may beperformed in multiple steps so as to prevent foaming and powdering.Additionally, the heating time is preferably from 3 minutes to 48 hours.The heating time longer than 48 hours is not preferred in terms ofproductivity. The heating time shorter than 3 minutes is not preferredbecause the imidization reaction, and the removal of the solvent may notsufficiently proceed.

The electrode thus obtained may be particularly suitably used as apositive electrode of a lithium ion secondary battery.

An electrode may be produced by

flow-casting or applying an electrode mixture paste onto a conductivecurrent collector such as copper, wherein the electrode mixture pastecomprises the binder resin composition for electrodes of the presentinvention, and an electrode active material which is capable ofreversibly incorporating and releasing lithium ion on charge anddischarge, for example, a carbon powder, a silicon powder, a tin powder,or a silicon-containing or tin-containing alloy powder; and then

heating the electrode mixture paste at a temperature of from 80° C. to300° C., more preferably from 120° C. to 280° C., particularlypreferably from 150° C. to 250° C., to remove a solvent and effectimidization.

When the heating temperature is lower than 80° C., the imidizationreaction may not sufficiently proceed, and the properties of the formedelectrode may be degraded. When the electrode mixture paste is heated ata temperature higher than 300° C., copper may deform, and therefore theproduct may not be used as an electrode. The heat treatment may beperformed in multiple steps so as to prevent foaming and powdering, inthis case, as well. Additionally, the heating time is preferably from 3minutes to 48 hours. The heating time longer than 48 hours is notpreferred in terms of productivity. The heating time shorter than 3minutes is not preferred because the imidization reaction, and theremoval of the solvent may not sufficiently proceed.

The electrode thus obtained may be particularly suitably used as anegative electrode of a lithium ion secondary battery.

The aqueous polyimide precursor solution composition of the presentinvention may also be suitably used as a polyimide precursor resincomposition for flexible device substrates.

According to the method for producing the flexible device of the presentinvention, a coating film of an aqueous polyimide precursor solutioncomposition layer is formed on a substrate by applying or spraying anaqueous polyimide precursor solution composition (specifically, anaqueous polyimide precursor solution composition in which a polyamicacid consisting of a repeating unit represented by the formula (1) ishomogeneously dissolved in an aqueous solvent together with an imidazolein an amount of 1.6 mole or more per mole of the tetracarboxylic acidcomponent of the polyamic acid) onto the substrate surface, and then theaqueous polyimide precursor solution composition is heated to provide apolyimide substrate for flexible devices.

According to the present invention, a polyimide substrate for flexibledevices may be suitably prepared by heating the aqueous polyimideprecursor solution composition to remove an aqueous solvent and effectimidization (dehydration/ring closure). The heat treatment conditionsare not limited, but, in general, the aqueous polyimide precursorsolution composition may be preferably heated at a temperature of 100°C. or higher, preferably from 120° C. to 600° C., more preferably from150° C. to 500° C., further preferably from 150° C. to 350° C., for from0.01 hours to 30 hours, preferably from 0.01 hours to 10 hours,preferably while increasing the temperature stepwise.

The heat treatment may be suitably performed under atmospheric pressure,and may be performed under reduced pressure so as to efficiently removethe aqueous solvent. The aqueous polyimide precursor solutioncomposition may be heated at a relatively low temperature under reducedpressure at the early stage for deaeration. When the heating temperatureis rapidly increased, a problem such as foaming may occur, and thereforea good flexible device substrate may not be obtained.

According to the method for producing the polyimide substrate forflexible devices of the present invention, the aqueous polyimideprecursor solution composition may be heated at a relatively lowtemperature (for example, 150° C. to 300° C., preferably 180° C. to 250°C.) to readily provide a polyimide substrate for flexible devices, whichhas excellent properties, and is in no way inferior to a polyimidesubstrate obtained from a commonly-used polyimide precursor (polyamicacid) solution composition comprising an organic solvent.

According to the method for producing the flexible device of the presentinvention, a solid polyimide resin film is formed on a carrier substrateas a support by applying a polyimide precursor resin composition(aqueous polyimide precursor solution composition) onto the carriersubstrate, and heating the composition; a circuit is formed on thepolyimide resin film; and then the polyimide resin film on which thecircuit is formed is separated from the carrier substrate.

Any method for applying an aqueous polyimide precursor solutioncomposition may be applied, as long as a coating film having a uniformthickness is formed on a carrier substrate (support). For example, diecoating, spin coating, and screen printing may be employed for theapplication.

A substrate for flexible devices may be suitably produced by a method,comprising

forming a coating film of an aqueous polyimide precursor solutioncomposition on a carrier substrate;

heating the coating film at a relatively low temperature to effect theremoval of the aqueous solvent, thereby forming a self-supporting film(the film in a state of not flowing; the polymerization and partialimidization reaction, as well as the removal of the aqueous solvent,proceed.); and

heating the self-supporting film on the substrate, or alternatively, theself-supporting film which is peeled from the substrate, if necessary,to effect dehydration/imidization.

The terms “removal of the aqueous solvent” and “dehydration/imidization”as used herein do not mean that only the removal of the aqueous solventproceeds and only the dehydration/imidization proceeds, respectively, inthe steps. In the aqueous solvent removal step, thedehydration/imidization proceeds to some extent. In thedehydration/imidization step, the removal of the residual aqueoussolvent proceeds.

The aqueous polyimide precursor solution composition of the presentinvention may contain other additive component(s) depending on theintended application of the polyimide substrate for flexible devicesobtained. Additionally, another resin layer may be laminated on thepolyimide substrate for flexible devices obtained.

In the method for producing the flexible device of the presentinvention, the thickness of the polyimide resin film is desirably from 1μm to 20 μm. When the thickness is less than 1 μm, the polyimide resinfilm may not remain adequately resistant, and therefore the polyimideresin film may not withstand stress and may be broken when used as aflexible device substrate. When the thickness of the polyimide resinfilm is more than 20 μm and greater, it may be difficult to achieve thethinning of the flexible device. The thickness of the polyimide resinfilm is more desirably from 2 μm to 10 μm so as to achieve the furtherthinning, while maintaining an adequate resistance for the flexibledevice.

According to the method for producing the flexible device of the presentinvention, a circuit needed for a display device or a light-receivingdevice is formed on the polyimide resin film formed as described above.This step differs from device to device. For example, in the case of theproduction of a TFT liquid crystal display device, a TFT of amorphoussilicon, for example, is formed on the polyimide resin film. The TFTcomprises a gate metal layer, a silicon nitride gate dielectric layer,and an ITI pixel electrode. In addition, a structure needed for a liquidcrystal display may be formed thereon by a known method. The method forforming a circuit, and the like is not limited because the polyimideresin film obtained according to the present invention has excellentproperties such as heat resistance, and toughness.

The polyimide resin film on which the circuit etc. is formed asdescribed above is separated from the carrier substrate. The method forthe separation is not limited. For example, the polyimide resin film onwhich the circuit is formed may be separated from the carrier substrateby irradiation with laser or the like from the carrier substrate side.Because the polyimide resin film obtained according to the presentinvention has high flexibility and toughness, it may be physicallyseparated from the carrier substrate (support) simply.

Examples of the flexible device in the present invention include displaydevices such as a liquid crystal display, an organic EL display and anelectronic paper, and light-receiving devices such as a solar cell andCMOS. The present invention may be particularly suitably applied todevices to be thinner and flexible.

EXAMPLES

Hereinafter, the present invention will be more specifically describedwith reference to Examples and Comparative Examples, but the presentinvention is not limited to these Examples.

The methods for measuring the properties, which was used in thefollowing examples, will be described below.

<Solid Content>

A sample solution (the weight is referred to as “w1”) was heated, at120° C. for 10 minutes, 250° C. for 10 minutes, and then 350° C. for 30minutes in a hot air dryer, and the weight of the sample after the heattreatment (the weight is referred to as “w2”) was measured. The solidcontent [wt %] was calculated by the following formula.

Solid content [wt %]=(w2/w1)×100

<Inherent Viscosity>

A sample solution was diluted to a concentration of 0.5 g/dl based onthe solid content (the solvent: water). The flowing time (T₁) of thediluted solution was measured at 30° C. using a Cannon-Fenske viscometerNo. 100. The inherent viscosity was calculated by the following formulausing the flowing time (T₀) of the blank water.

Inherent viscosity={ln(T ₁ /T ₀)}/0.5

<Solution Viscosity (Rotational Viscosity)>

The solution viscosity was measured at 30° C. using an E type viscometermanufactured by Tokimec, Inc.

<Preparation of Sample of Polyimide Film>

An aqueous polyimide precursor solution composition obtained was appliedon a glass plate as a substrate with a bar coater. The resulting coatingfilm was deaerated and predried at 25° C. for 30 minutes under reducedpressure. Subsequently, the predried coating film was placed into a hotair dryer and heated at 80° C. for 30 minutes, and then 200° C. for 1hour under atmospheric pressure, to provide a polyimide film having athickness of 25 μm. The properties of the polyimide film, wereevaluated.

<Mechanical Properties (Tensile Test)>

The tensile test was performed in accordance with ASTM D882 using atensile tester (RTC-1225A, manufactured by Orientec Co., Ltd.) todetermine the tensile elastic modulus, tensile elongation at break, andtensile strength at break.

<Evaluation of Flexibility (Bendability)>

The 180° folding test was performed, and an article in which no crackappeared in the polyimide film was evaluated as ◯, and an article inwhich a crack appeared in the polyimide film was evaluated as ×.

<Production of Polyimide Seamless Belt>

An aqueous polyimide precursor solution composition was uniformlyapplied on the inner surface of a cylindrical mold having an insidediameter of 150 mm and a length of 300 mm, while rotating the mold at100 rpm. Subsequently, the resulting coating film was heated at 80° C.for 30 minutes, and then 200° C. for 1 hour, while rotating the mold at200 rpm, to provide a polyimide seamless belt having a thickness of 50μm.

The state of the seamless belt obtained was visually observed.Additionally, the properties of the polyimide seamless belt wereevaluated.

<Observation of State of Polyimide Seamless Belt>

An article in which no defects such as foaming and crack were observedwas evaluated as ◯, and an article in which defects such as foaming andcrack were observed in not less than 30% of the whole area was evaluatedas ×.

<Flexibility Test on Polyimide Seamless Belt>

The polyimide seamless belt sample obtained from the aqueous polyimideprecursor solution composition and having a thickness of 50 μm was cutinto a 10 mm×50 mm rectangle. The 180° folding test was repeated, andthe number of times the 180° folding test was repeated until a crackappeared was determined.

<Preparation of Sample of Binder Polyimide Film for Electrodes>

A binder resin composition for electrodes obtained was applied on aglass plate as a substrate with a bar coater. The resulting coating filmwas deaerated and predried at 25° C. for 30 minutes under reducedpressure. Subsequently, the predried coating film was placed into a hotair dryer and heated at 80° C. for 30 minutes, and then 200° C. for 1hour under atmospheric pressure, to provide a polyimide film having athickness of 25 μm. The properties of the polyimide film were evaluated.

<Swelling Test>

The polyimide film obtained from the binder resin composition forelectrodes was cut into a 5 cm square (thickness: 25 μm), which was usedas a sample. The sample was dried at 60° C. for 24 hours under vacuum,and the weight of the sample was defined as “dry weight (Wd)”. Thesample was immersed in a dimethyl carbonate (DMC) solution or a 10 wt %lithium methoxide methanol solution at 25° C. for 24 hours, and theweight of the sample was defined as “wet weight (Ww)”. The “swellingrate (S)” was calculated by the following formula.

S [wt %]=(Ww−Wd)/Ww×100

<Observation of State of Flexible Device Substrate>

An article in which no defects such as foaming and crack were observedwas evaluated as ◯, and an article in which defects such as foaming andcrack were observed in more than 30% of the whole area was evaluated as×.

The abbreviations of the compounds used in the following examples are asfollows:

-   s-BPDA: 3,3,4,4′-biphenyltetracarboxylic dianhydride-   ODPA: 4,4′-oxydiphthalic dianhydride-   t-DCDA: trans-dicyclohexyl-3,3′,4,4′-tetracarboxylic dianhydride-   H-PMDA: 1,2,4,5-cyclohexane tetracarboxylic-1,2:4,5-dianhydride-   6FDA: 4,4′-(hexafluoroisopropylidene)diphthalic anhydride-   ODA: 4,4′-diaminodiphenyl ether (solubility in water at 25° C.: 0.19    g/L)-   PPD: p-phenylenediamine (solubility in water at 25° C.: 120 g/L)-   t-CHDA: trans-1,4-diaminocyclobexane (solubility in water at 25° C.:    1000 g/L, molecular weight: 114)-   HMD: 1,6-hexamethylene diamine (solubility in water at 25° C.: 1000    g/L, molecular weight: 116)-   DMD: 1,10-decamethylene diamine (solubility in water at 25° C.: 1000    g/L, molecular weight: 172)-   D400: JEFFAMINE D400 (manufactured by Mitsui Chemicals, Inc.,    diamine compound having a weight average molecular weight of 435)-   D2000: JEFFAMINE D2000 (manufactured by Mitsui Chemicals, Inc.,    diamine compound having a weight average molecular weight of 2041)-   1074: PRIAMINE 1074 (manufactured by Croda Japan KK, diamine    compound having a weight average molecular weight of 548)-   1,2-DMZ: 1,2-dimethylimidazole (solubility in water at 25° C.: 239    g/L)-   NMP: N-methyl-2-pyrrolidone

Example A1

In a 500 mL (internal volume) glass reaction vessel equipped with astirrer and a nitrogen-gas charging/discharge tube was placed 400 g ofwater as a solvent. And then, 16.03 g (0.148 mol) of PPD and 11.29 g(0.099 mol) of t-CHDA, and 59.38 g (1.25 equivalents per carboxyl group)of 1,2-DMZ were added thereto, and the mixture was stirred at 25° C. for1 hour to dissolve these compounds in water. Subsequently, 72.68 g(0.247 mol) of s-BPDA was added to the resulting solution, and themixture was stirred at 70° C. for 6 hours to provide an aqueouspolyimide precursor solution having a solid content of 16.7 wt %, asolution viscosity of 27.2 Pa·s, and an inherent viscosity of 1.04.

The properties of the aqueous polyimide precursor solution compositionand the polyimide film obtained are shown in Table 1.

Example A2

In a 500 mL (internal volume) glass reaction vessel equipped with astirrer and a nitrogen-gas charging/discharge tube was placed 400 g ofwater as a solvent. And then, 21.63 g (0.108 mol) of ODA and 7.98 g(0.046 mol) of DMD, and 37.09 g (1.25 equivalents per carboxyl group) of1,2-DMZ were added thereto, and the mixture was stirred at 25° C. for 1hour to dissolve these compounds in water. Subsequently, 45.40 g (0.154mol) of s-BPDA was added to the resulting solution, and the mixture wasstirred at 70° C. for 6 hours to provide an aqueous polyimide precursorsolution having a solid content of 13.0 wt %, a solution viscosity of54.5 Pa·s, and an inherent viscosity of 0.28.

The properties of the aqueous polyimide precursor solution compositionand the polyimide film obtained are shown in Table 1.

Example A3

In a 500 mL (internal volume) glass reaction vessel equipped with astirrer and a nitrogen-gas charging/discharge tube was placed 400 g ofwater as a solvent. And then, 17.96 g (0.166 mol) of PPD and 12.26 g(0.071 mol) of DMD, and 57.01 g (1.25 equivalents per carboxyl group) of1,2-DMZ were added thereto, and the mixture was stirred at 25° C. for 1hour to dissolve these compounds in water. Subsequently, 69.78 g (0.237mop of s-BPDA was added to the resulting solution, and the mixture wasstirred at 70° C. for 6 hours to provide an aqueous polyimide precursorsolution having a solid content of 16.2 wt %, a solution viscosity of30.8 Pa·s, and an inherent viscosity of 0.86.

The properties of the aqueous polyimide precursor solution compositionand the polyimide film obtained are shown in Table 1.

Example A4

In a 500 mL (internal volume) glass reaction vessel equipped with astirrer and a nitrogen-gas charging/discharge tube was placed 400 g ofwater as a solvent. And then, 22.21 g (0.111 mol) of ODA, 4.80 g (0.044mol) of PPD and 7.73 g (0.067 mol) of HMD, and 53.32 g (1.25 equivalentsper carboxyl group) of 1,2-DMZ were added thereto, and the mixture wasstirred at 25° C. for 1 hour to dissolve these compounds in water.Subsequently, 65.26 g (0.222 mol) of s-BPDA was added to the resultingsolution, and the mixture was stirred at 70° C. for 6 hours to providean aqueous polyimide precursor solution having a solid content of 16.7wt %, a solution viscosity of 20.7 Pa·s, and an inherent viscosity of0.38.

The properties of the aqueous polyimide precursor solution compositionand the polyimide film obtained are shown in Table 1.

Example A5

In a 500 mL (internal volume) glass reaction vessel equipped with astirrer and a nitrogen-gas charging/discharge tube was placed 400 g ofwater as a solvent. And then, 18.70 g (0.173 mol) of PPD and 8.61 g(0.074 mol) of HMD, and 59.38 g (1.25 equivalents per carboxyl group) of1,2-DMZ were added thereto, and the mixture was stirred at 25° C. for 1hour to dissolve these compounds in water. Subsequently, 72.68 g (0.247mol) of s-BPDA was added to the resulting solution, and the mixture wasstirred at 70° C. for 6 hours to provide an aqueous polyimide precursorsolution having a solid content of 16.1 wt %, a solution viscosity of30.2 Pa·s, and an inherent viscosity of 0.82.

The properties of the aqueous polyimide precursor solution compositionand the polyimide film obtained are shown in Table 1.

Example A6

In a 500 mL (internal volume) glass reaction vessel equipped with astirrer and a nitrogen-gas charging/discharge tube was placed 425 g ofwater as a solvent. And then, 19.42 g (0,097 mol) of ODA, 3.50 g (0.032mol) of PPD and 3.76 g (0.032 mol) of HMD, and 38.85 g (1.25 equivalentsper carboxyl group) of 1,2-DMZ were added thereto, and the mixture wasstirred at 25° C. for 1 hour to dissolve these compounds in water.Subsequently, 33.29 g (0.113 mol) of s-BPDA and 15.04 g (0.048 mol) ofODPA was added to the resulting solution, and the mixture was stirred at70° C. for 6 hours to provide an aqueous polyimide precursor solutionhaving a solid content of 13.1 wt %, a solution viscosity of 54.8 Pa·s,and an inherent viscosity of 0.46.

The properties of the aqueous polyimide precursor solution compositionand the polyimide film obtained are shown in Table 1.

Example A7

In a 500 mL (internal volume) glass reaction vessel equipped with astirrer and a nitrogen-gas charging/discharge tube was placed 425 g ofwater as a solvent. And then, 19.29 g (0.096 mol) of ODA, 3.47 g (0.032mol) of PPD and 3.73 g (0.032 mol) of HMD, and 38.58 g (1.25 equivalentsper carboxyl group) of 1,2-DMZ were added thereto, and the mixture wasstirred at 25° C. for 1 hour to dissolve these compounds in water.Subsequently, 23.61 g (0.080 mol) of s-BPDA and 24.90 g (0.080 mol) ofODPA was added to the resulting solution, and the mixture was stirred at70° C. for 6 hours to provide an aqueous polyimide precursor solutionhaving a solid content of 13.0 wt %, a solution viscosity of 20.1 Pa·s,and an inherent viscosity of 0.42.

The properties of the aqueous polyimide precursor solution compositionand the polyimide film obtained are shown in Table 1.

Example A8

In a 500 mL (internal volume) glass reaction vessel equipped with astirrer and a nitrogen-gas charging/discharge tube was placed 400 g ofwater as a solvent. And then, 26.10 g (0.130 mol) of ODA and 6.30 g(0.014 mol) of JEFFAMINE D400, and 34.81 g (1.25 equivalents percarboxyl group) of 1,2-DMZ were added thereto, and the mixture wasstirred at 25° C. for 1 hour to dissolve these compounds in water.Subsequently, 42.61 g (0.145 mol) of s-BPDA was added to the resultingsolution, and the mixture was stirred at 70° C. for 6 hours to providean aqueous polyimide precursor solution having a solid content of 12.4wt %, a solution viscosity of 38.7 Pa·s, and an inherent viscosity of0.27.

The properties of the aqueous polyimide precursor solution compositionand the polyimide film obtained are shown in Table 1.

Example A9

In a 500 mL (internal volume) glass reaction vessel equipped with astirrer and a nitrogen-gas charging/discharge tube was placed 400 g ofwater as a solvent. And then, 26.64 g (0.246 mol) of PPD, and 59.20 g(1.25 equivalents per carboxyl group) of 1,2-DMZ were added thereto, andthe mixture was stirred at 25° C. for 1 hour to dissolve these compoundsin water. Subsequently, 50.73 g (0.172 mol) of s-BPDA and 22.63 g (0.074mol) of t-DCDA was added to the resulting solution, and the mixture wasstirred at 70° C. for 6 hours to provide an aqueous polyimide precursorsolution having a solid content of 16.2 wt %, a solution viscosity of107.5 Pa·s, and an inherent viscosity of 0.87.

The properties of the aqueous polyimide precursor solution compositionand the polyimide film obtained are shown in Table 1.

Example A10

In a 500 mL (internal volume) glass reaction vessel equipped with astirrer and a nitrogen⁻gas charging/discharge tube was placed 400 g ofwater as a solvent. And then, 28.36 g (0.262 mol) of PPD, and 63.03 g(1.25 equivalents per carboxyl group) of 1,2-DMZ were added thereto, andthe mixture was stirred at 25° C. for 1 hour to dissolve these compoundsin water. Subsequently, 54.00 g (0.184 mol) of s-BPDA and 17.63 g (0.079mol) of H-PMDA was added to the resulting solution, and the mixture wasstirred at 70° C. for 6 hours to provide an aqueous polyimide precursorsolution having a solid content of 16.5 wt %, a solution viscosity of8.7 Pa·s, and an inherent viscosity of 0.60.

The properties of the aqueous polyimide precursor solution compositionand the polyimide film obtained are shown in Table 1.

Example A11

In a 500 mL (internal volume) glass reaction vessel equipped with astirrer and a nitrogen-gas charging/discharge tube was placed 425 g ofwater as a solvent. And then, 20.47 g (0.102 mol) of ODA and 5.00 g(0.044 mol) of t-CHDA, and 35.10 g (1.25 equivalents per carboxyl group)of 1,2-DMZ were added thereto, and the mixture was stirred at 25° C. for1 hour to dissolve these compounds in water. Subsequently, 30.07 g(0.102 mol) of s-BPDA and 19.46 g (0.044 mol) of 6FDA was added to theresulting solution, and the mixture was stirred at 70° C. for 6 hours toprovide an aqueous polyimide precursor solution having a solid contentof 13.2 wt %, a solution viscosity of 5.3 Pa·s, and an inherentviscosity of 0.35.

The properties of the aqueous polyimide precursor solution compositionand the polyimide film obtained are shown in Table 1-2.

Example A12

In a 500 mL (internal volume) glass reaction vessel equipped with astirrer and a nitrogen-gas charging/discharge tube was placed 425 g ofwater as a solvent. And then, 20.54 g (0.102 mol) of ODA and 4.75 g(0.044 mol) of PPD, and 35.10 g (1.25 equivalents per carboxyl group) of1,2-DMZ were added thereto, and the mixture was stirred at 25° C. for 1hour to dissolve these compounds in water. Subsequently, 30.18 g (0.102mol) of s-BPDA and 19.53 g (0.044 mol) of 6FDA was added to theresulting solution, and the mixture was stirred at 70° C. for 6 hours toprovide an aqueous polyimide precursor solution having a solid contentof 13.1 wt %, a solution viscosity of 7.5 Pa·s, and an inherentviscosity of 0.42.

The properties of the aqueous polyimide precursor solution compositionand the polyimide film obtained are shown in Table 1-2.

Reference Example A1

In a 500 mL (internal volume) glass reaction vessel equipped with astirrer and a nitrogen-gas charging/discharge tube was placed 400 g ofwater as a solvent. And then, 9.37 g (0.047 mol) of ODA and 21.76 g(0.187 mol) of HMD, and 56.26 g (1.25 equivalents per carboxyl group) of1,2-DMZ were added thereto, and the mixture was stirred at 25° C. for 1hour to dissolve these compounds in water. Subsequently, 68.87 g (0.234mol) of s-BPDA was added to the resulting solution, and the mixture wasstirred at 70° C. for 6 hours to provide an aqueous polyimide precursorsolution having a solid content of 16.0 wt %, a solution viscosity of0.7 Pa·s, and an inherent viscosity of 0.72.

The properties of the aqueous polyimide precursor solution compositionand the polyimide film obtained are shown in Table 2.

Reference Example A2

In a 500 mL (internal volume) glass reaction vessel equipped with astirrer and a nitrogen-gas charging/discharge tube was placed 400 g ofwater as a solvent. And then, 5.29 g (0.049 mol) of PPD and 22.74 g(0.196 mol) of HMD, and 58.80 g (1.25 equivalents per carboxyl group) of1,2-DMZ were added thereto, and the mixture was stirred at 25° C. for 1hour to dissolve these compounds in water. Subsequently, 71.97 g (0.245mol) of s-BPDA was added to the resulting solution, and the mixture wasstirred at 70° C. for 6 hours to provide an aqueous polyimide precursorsolution having a solid content of 15.7 wt %, a solution viscosity of1.4 Pa·s, and an inherent viscosity of 0.86.

The properties of the aqueous polyimide precursor solution compositionand the polyimide film obtained are shown in Table 2.

Comparative Example A1

In a 500 mL (internal volume) glass reaction vessel equipped with astirrer and a nitrogen-gas charging/discharge tube was placed 400 g ofwater as a solvent. And then, 26.56 g (0.133 mol) of ODA and 30.08 g(0.015 mol) of JEFFAMINE D2000, and 35.43 g (1.25 equivalents percarboxyl group) of 1,2-DMZ were added thereto, and the mixture wasstirred at 25° C. for 1 hour to dissolve these compounds in water.Subsequently, 43.36 g (0.147 mol) of s-BPDA was added to the resultingsolution, and the mixture was stirred at 70° C. for 6 hours. Still,s-BPDA was not dissolved therein homogeneously, and an aqueous polyimideprecursor solution composition could not be obtained.

The results are shown in Table 2.

Comparative Example A2

In a 500 mL (internal volume) glass reaction vessel equipped with astirrer and a nitrogen-gas charging/discharge tube was placed 400 g ofwater as a solvent. And then, 34.06 g (0.170 mol) of ODA and 10.34 g(0.019 mol) of PRIAMINE 1074, and 45.42 g (1.25 equivalents per carboxylgroup) of 1,2-DMZ were added thereto, and the mixture was stirred at 25°C. for 1 hour to dissolve these compounds in water. Subsequently, 55.60g (0.189 mol) of s-BPDA was added to the resulting solution, and themixture was stirred at 70° C. for 6 hours. Still, s-BPDA was notdissolved therein homogeneously, and an aqueous polyimide precursorsolution composition could not be obtained.

The results are shown in Table 2.

TABLE 1 Composition of aqueous poly- Exam- Exam- Exam- Exam- Exam- Exam-Exam- Exam- Exam- Exam- imide precursor solution ple A1 ple A2 ple A3ple A4 ple A5 ple A6 ple A7 ple A8 ple A9 ple A10 acid s-BPDA (mol %)100 100 100 100 100 70 50 100 70 70 component ODPA (mol %) 30 50 t-DCDA(mol %) 30 H-PMDA (mol %) 30 diamine ODA (mol %) 70 50 60 60 90component PPD (mol %) 60 70 20 70 20 20 100 100 t-CHDA (mol %) 40 DMD(mol %) 30 30 HMD (mol %) 30 30 20 20 D400 (mol %) 10 imidazole 1,2-DMZ(equivalents) 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 Aqueouspolymerization temperature 70 70 70 70 70 70 70 70 70 70 polyimidepolymerization time 6 6 6 6 6 6 6 6 6 6 precursor inherent viscosity1.04 0.28 0.86 0.38 0.82 0.46 0.42 0.27 0.87 0.60 solution solid content(wt %) 16.7 13.0 16.2 16.7 16.1 13.1 13.0 12.4 16.2 16.5 solutionviscosity (Pa · s) 27.2 54.5 30.8 20.7 30.2 54.8 20.1 38.7 107.5 8.7Properties evaluation of flexibility ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ of polyimidetensile elastic modulus (GPa) 5.2 3.0 4.1 2.8 4.9 3.3 3.4 3.2 5.0 5.6tensile elongation at break (%) 20 27 25 38 41 90 75 27 30 18 tensilestrength at break (MPa) 180 124 133 135 167 156 152 127 145 208

TABLE 1-2 Example Example A11 A12 Composition of aqueous polyimideprecursor solution acid s-BPDA (mol %) 70 70 component ODPA (mol %)t-DCDA (mol %) H-PMDA (mol %) 6FDA (mol %) 30 30 diamine ODA (mol %) 7070 component PPD (mol %) 30 t-CHDA (mol %) 30 DMD (mol %) HMD (mol %)D400 (mol %) imidazole 1,2-DMZ (equivalents) 1.25 1.25 Aqueous polyimideprecursor solution polymerization temperature 70 70 polymerization time6 6 inherent viscosity 0.35 0.42 solid content (wt %) 13.2 13.1 solutionviscosity (Pa · s) 5.3 7.5 Properties of polyimide evaluation offlexibility ◯ ◯ tensile elastic modulus (GPa) 2.9 3.3 tensile elongationat break (%) 28 42 tensile strength at break (MPa) 124 139

TABLE 2 Reference Reference Comparative Comparative Example A1 ExampleA2 Example A1 Example A2 Composition of aqueous polyimide precursorsolution acid s-BPDA (mol %) 100 100 100 100 component diamine ODA (mol%) 20 90 90 component PPD (mol %) 20 HMD (mol %) 80 80 D2000 (mol %) 101074 (mol %) 10 imidazole 1,2-DMZ (equivalents) 1.25 1.25 1.25 1.25Aqueous polyimide precursor solution polymerization temperature 70 70 7070 polymerization time 6 6 6 6 inherent viscosity 0.72 0.86 Aqueouspolyimide precursor solid content (wt %) 16.0 15.7 solution could not beobtained. solution viscosity (Pa · s) 0.7 1.4 (not homogeneouslydissolved) Properties of polyimide tensile elastic modulus (GPa) 3.0 2.8tensile elongation at break (%) 17 27 tensile strength at break (MPa)110 102

Example B1

A polyimide seamless belt was prepared from the aqueous polyimideprecursor solution composition obtained in Example A1, as described in<Production of Polyimide Seamless Belt> section.

The results of the state observations and the properties evaluations ofthe aqueous polyimide precursor solution composition and the polyimideseamless belt obtained are shown in Table 3.

Example B2

A polyimide seamless belt was prepared from the aqueous polyimideprecursor solution composition obtained in Example A4, as described in<Production of Polyimide Seamless Belt> section.

The results of the state observations and the properties evaluations ofthe aqueous polyimide precursor solution composition and the polyimideseamless belt obtained are shown in Table 3.

Example B3

A polyimide seamless belt was prepared from the aqueous polyimideprecursor solution composition obtained in Example A6, as described in<Production of Polyimide Seamless Belt> section.

The results of the state observations and the properties evaluations ofthe aqueous polyimide precursor solution composition and the polyimideseamless belt obtained are shown in Table 3.

Example B4

A polyimide seamless belt was prepared from the aqueous polyimideprecursor solution composition obtained in Example A7, as described in<Production of Polyimide Seamless Belt> section.

The results of the state observations and the properties evaluations ofthe aqueous polyimide precursor solution composition and the polyimideseamless belt obtained are shown in Table 3.

Reference Example B1

In a 500 mL (internal volume) glass reaction vessel equipped with astirrer and a nitrogen-gas charging/discharge tube was placed 450 g ofwater as a solvent. And then, 20.25 g (0.101 mol) of ODA and 24.31 g(1.25 equivalents per carboxyl group) of 1,2-DMZ were added thereto, andthe mixture was stirred at 25° C. for 1 hour to dissolve these compoundsin water. Subsequently, 29.75 g (0.101 mol) of s-BPDA was added to theresulting solution, and the mixture was stirred at 70° C. for 4 hours toprovide an aqueous polyimide precursor solution having a solid contentof 8.7 wt %, a solution viscosity of 32.0 Pa·s, and an inherentviscosity of 0.42.

An aromatic polyimide seamless belt was prepared from the aqueouspolyimide precursor solution composition, as described in <Production ofAromatic Polyimide Seamless Belt> section.

The results of the state observations and the properties evaluations ofthe aqueous polyimide precursor solution composition and the polyimideseamless belt obtained are shown in Table 3.

Reference Example B2

In a 500 mL (internal volume) glass reaction vessel equipped with astirrer and a nitrogen-gas charging/discharge tube was placed 450 g ofwater as a solvent. And then, 14.86 g (0.074 mol) of ODA, 3.44 g (0.032mol) of PPD and 20.43 g (1.25 equivalents per carboxyl group) of 1,2-DMZwere added thereto, and the mixture was stirred at 25° C. for 1 hour todissolve these compounds in water. Subsequently, 21.83 g (0.074 mol) ofs-BPDA and 9.87 g (0.032 mop of ODPA were added to the resultingsolution, and the mixture was stirred at 70° C. for 4 hours to providean aqueous polyimide precursor solution composition having a solidcontent of 9.0 wt %, a solution viscosity of 5.2 Pa·s, and an inherentviscosity of 0.46.

An aromatic polyimide seamless belt was prepared from the aqueouspolyimide precursor solution composition, as described in <Production ofAromatic Polyimide Seamless Belt> section.

The results of the state observations and the properties evaluations ofthe aqueous polyimide precursor solution composition and the polyimideseamless belt obtained are shown in Table 3.

TABLE 3 Composition of aqueous poly- Exam- Exam- Exam- Exam- ReferenceReference imide precursor solution ple B1 ple B2 ple B3 ple B4 ExampleB1 Example B2 acid s-BPDA (mol %) 100 100 70 50 100 70 component ODPA(mol %) 30 50 30 diamine ODA (mol %) 50 60 60 100 70 component PPD (mol%) 60 20 20 20 30 t-CHDA (mol %) 40 HMD (mol %) 30 20 20 imidazole1,2-DMZ (equivalents) 1.25 1.25 1.25 1.25 1.25 1.25 Aqueouspolymerization temperature 70 70 70 70 70 70 polyimide polymerizationtime 6 6 6 6 4 4 precursor inherent viscosity 1.04 0.38 0.46 0.42 0.420.46 solution solid content (wt %) 16.7 16.7 13.1 13.0 8.7 9.0 solutionviscosity (Pa · s) 27.2 20.7 54.8 20.1 32.0 5.2 Polyimide stateobservation ◯ ◯ ◯ ◯ ◯ ◯ seamless flexibility test (number of times) 7075 85 82 35 50 belt tensile elastic modulus (GPa) 5.0 2.9 3.1 3.4 3.43.9 tensile elongation at break (%) 18 32 75 68 28 27 tensile strengthat break (MPa) 178 128 145 142 160 154

Example C1

In a mortar, 4.79 g of the aqueous polyimide precursor solutioncomposition (binder resin composition for electrodes) obtained inExample A2 (solid content after imidization: 0.8 g) and 9.2 g of 300mesh silicon powder were ground and kneaded to provide an electrodemixture paste. The obtained paste was capable of being spread on acopper foil with a glass rod. The copper foil on which the paste wasapplied was fixed on a substrate, and heated at 120° C. for 1 hour, 200°C. for 10 minutes, 220° C. for 10 minutes, and then 250° C. for 10minutes in a nitrogen atmosphere, to suitably provide an electrodehaving an active material layer thickness of 100 μm.

The properties of the binder resin composition for electrodes and thepolyimide binder for electrodes obtained are shown in Table 4.

Example C2

An electrode was suitably prepared from the aqueous polyimide precursorsolution composition (binder resin composition for electrodes) obtainedin Example A4 in the same way as in Example C1.

The properties of the binder resin composition for electrodes and thepolyimide binder for electrodes obtained are shown in Table 4.

Example C3

An electrode was suitably prepared from the aqueous polyimide precursorsolution composition (hinder resin composition for electrodes) obtainedin Example A5 in the same way as in Example C1.

The properties of the binder resin composition for electrodes and thepolyimide binder for electrodes obtained are shown in Table 4.

Example C4

An electrode was suitably prepared from the aqueous polyimide precursorsolution composition (binder resin composition for electrodes) obtainedin Example A6 in the same way as in Example C1.

The properties of the binder resin composition for electrodes and thepolyimide binder for electrodes obtained are shown in Table 4.

Example C5

An electrode was suitably prepared from the aqueous polyimide precursorsolution composition (binder resin composition for electrodes) obtainedin Example A7 in the same way as in Example C1.

The properties of the binder resin composition for electrodes and thepolyimide binder for electrodes obtained are shown in Table 4.

TABLE 4 Composition of binder resin Exam- Exam- Exam- Exam- Exam-composition for electrodes ple C1 ple C2 ple C3 ple C4 ple C5 acids-BPDA (mol %) 100 100 100 70 50 component ODPA (mol %) 30 50 diamineODA (mol %) 70 50 60 60 component PPD (mol %) 20 70 20 20 DMD (mol %) 30HMD (mol %) 30 30 20 20 imidazole 1,2-DMZ (equivalents) 1.25 1.25 1.251.25 1.25 Aqueous polymerization temperature 70 70 70 70 70 polyimidepolymerization time 6 6 6 6 6 precursor inherent viscosity 0.28 0.380.82 0.46 0.42 solution solid content (wt %) 13.0 16.7 16.1 13.1 13.0solution viscosity (Pa · s) 54.5 20.7 30.2 54.8 20.1 Properties tensileelastic modulus (GPa) 3.0 2.8 4.9 3.3 3.4 of polyimide tensileelongation at break (%) 27 38 41 90 75 binder for tensile strength atbreak (MPa) 124 135 167 156 152 electrodes DMC swelling rate (%) 0.8 0.30.5 0.1 0.2 lithium methoxide solution swelling rate (%) 0.6 0.8 1.1 0.70.9

Example D1

The aqueous polyimide precursor solution composition obtained in ExampleA1 was applied on a glass plate as a substrate with a bar coater. Theresulting coating film was deaerated and predried at 25° C. for 30minutes under reduced pressure. Subsequently, the predried coating filmwas placed into a hot air dryer and heated at 80° C. for 30 minutes,120° C. for 30 minutes, 200° C. for 10 minutes, and then 250° C. for 10minutes under atmospheric pressure, to provide a polyimide film having athickness of 10 μm.

The results of the state observations and the properties evaluations ofthe aqueous polyimide precursor solution composition and the polyimidesubstrate for flexible devices obtained are shown in Table 5.

Example D2

The aqueous polyimide precursor solution composition obtained in ExampleAS was applied on a glass plate as a substrate with a bar coater. Theresulting coating film was deaerated and predried at 25° C. for 30minutes under reduced pressure. Subsequently, the predried coating filmwas placed into a hot air dryer and heated at 80° C. for 30 minutes,120° C. for 30 minutes, 200° C. for 10 minutes, and then 250° C. for 10minutes under atmospheric pressure, to provide a polyimide film having athickness of 10 μm.

The results of the state observations and the properties evaluations ofthe aqueous polyimide precursor solution composition and the polyimidesubstrate for flexible devices obtained are shown in Table 5.

Example D3

The aqueous polyimide precursor solution composition obtained in ExampleA9 was applied on a glass plate as a substrate with a bar coater. Theresulting coating film was deaerated and predried at 25° C. for 30minutes under reduced pressure. Subsequently, the predried coating filmwas placed into a hot air dryer and heated at 80° C. for 30 minutes,120° C. for 30 minutes, 200° C. for 10 minutes, and then 250° C. for 10minutes under atmospheric pressure, to provide a polyimide film having athickness of 10 μm.

The results of the state observations and the properties evaluations ofthe aqueous polyimide precursor solution composition and the polyimidesubstrate for flexible devices obtained are shown in Table 5.

Example D4

The aqueous polyimide precursor solution composition obtained in ExampleA10 was applied on a glass plate as a substrate with a bar coater. Theresulting coating film was deaerated and predried at 25° C. for 30minutes under reduced pressure. Subsequently, the predried coating filmwas placed into a hot air dryer and heated at 80° C. for 30 minutes,120° C. for 30 minutes, 200° C. for 10 minutes, and then 250° C. for 10minutes under atmospheric pressure, to provide a polyimide film having athickness of 10 μm.

The results of the state observations and the properties evaluations ofthe aqueous polyimide precursor solution composition and the polyimidesubstrate for flexible devices obtained are shown in Table 5.

TABLE 5 Example D1 Example D2 Example D3 Example D4 Composition ofaqueous polyimide precursor solution acid s-BPDA (mol %) 100 100 70 70component t-DCDA (mol %) 30 H-PMDA (mol %) 30 diamine PPD (mol %) 60 70100 100 component t-CHDA (mol %) 40 HMD (mol %) 30 imidazole 1,2-DMZ(equivalents) 1.25 1.25 1.25 1.25 Aqueous polyimide precursor solutionpolymerization temperature 70 70 70 70 polymerization time 6 6 6 6inherent viscosity 1.04 0.82 0.87 0.60 solid content (wt %) 16.7 16.116.2 16.5 solution viscosity (Pa · s) 27.2 30.2 107.5 8.7 Properties ofsubstrate for flexible devices state observation ◯ ◯ ◯ ◯ tensile elasticmodulus (GPa) 5.7 5.4 5.5 6.1 tensile elongation at break (%) 18 30 2415 tensile strength at break (MPa) 175 164 150 185

According to the present invention, there may be provided a method foreasily producing an aqueous polyimide precursor solution composition,which has higher environmental acceptability, without the need for asolvent other than water. According to the production method, an aqueouspolyimide precursor solution composition having an extremely low organicsolvent content, particularly an aqueous polyimide precursor solutioncomposition comprising an aqueous solvent which contains no organicsolvent, may be very easily (directly) produced.

According to the present invention, there may be provided an aqueouspolyimide precursor solution composition which comprises an aqueoussolvent and has good environmental acceptability, and may provide apolyimide having excellent properties such as flexibility, heatresistance, mechanical strength, electrical properties, and solventresistance, and preferably comprises a polyimide precursor having a highmolecular weight and a solvent containing no organic solvent other thanwater.

According to the present invention, there may be provided a method forproducing a polyimide seamless belt using an aqueous polyimide precursorsolution composition which comprises an aqueous solvent and has goodenvironmental acceptability. Moreover, the seamless belt of thepolyimide which is obtained according to the production method of thepresent invention may have excellent properties such as flexibility,heat resistance, mechanical strength, electrical properties, and solventresistance, and therefore may be suitably used as an intermediatetransfer seamless belt or a fixing seamless belt of anelectrophotographic device.

According to the present invention, there may be also provided a binderresin composition for electrodes which comprises an aqueous solvent andhas good environmental acceptability. Moreover, the polyimide obtainedfrom the binder resin composition for electrodes may have excellentproperties such as flexibility, heat resistance, mechanical strength,electrical properties, and solvent resistance, and have a low degree ofswelling in a battery environment, and have excellent toughness.

According to the present invention, there may be also provided apolyimide precursor resin composition for flexible device substrates,which comprises an aqueous solvent and has good environmentalacceptability. Moreover, the polyimide substrate for flexible devicewhich is obtained according to the present invention may have excellentproperties such as flexibility, heat resistance, mechanical strength,electrical properties, and solvent resistance, and therefore may besuitably used, for example, as a substrate for flexible device which isa display device such as substrates for a liquid crystal display, anorganic EL display and an electronic paper, and as a substrate forflexible device which is a light-receiving device such as a substratefor a thin-film solar cell.

What is claimed is:
 1. An aqueous polyimide precursor solution composition, wherein a polyamic acid, which is formed by the reaction of a tetracarboxylic acid component and a diamine component, and consists of a repeating unit represented by the following formula (1), is dissolved in an aqueous solvent together with an imidazole in an amount of 1.6 mole or more per mole of the tetracarboxylic acid component of the polyamic acid, wherein the aqueous polyimide precursor solution composition contains no organic solvent, and

the polyamic acid has an inherent viscosity of 0.2 or more. wherein A represents at least one group selected from the group consisting of a tetravalent group of an aromatic tetracarboxylic acid containing no fluorine group from which carboxyl groups have been removed, a tetravalent group of an aliphatic tetracarboxylic acid from which carboxyl groups have been removed, and a tetravalent group of an aromatic tetracarboxylic acid containing a fluorine group from which carboxyl groups have been removed, and B represents at least one group selected from the group consisting of a divalent group of an aromatic diamine containing no fluorine group and having a solubility in water at 25° C. of 0.1 g/L or more from which amino groups have been removed, a divalent group of an aliphatic diamine having a molecular weight of 500 or less from which amino groups have been removed, and a divalent group of an aromatic diamine containing a fluorine group, from which amino groups have been removed, with the proviso that more than 50 mol % of A is a tetravalent group of an aromatic tetracarboxylic acid containing no fluorine group from which carboxyl groups have been removed, and less than 50 mol %, including 0 mol %, of A is a tetravalent group of an aliphatic tetracarboxylic acid from which carboxyl groups have been removed, and/or a tetravalent group of an aromatic tetracarboxylic acid containing a fluorine group from which carboxyl groups have been removed, and more than 50 mol % of B is a divalent group of an aromatic diamine containing no fluorine group and having a solubility in water at 25° C. of 0.1 g/L or more from which amino groups have been removed, and less than 50 mol %, including 0 mol %, of B is a divalent group of an aliphatic diamine having a molecular weight of 500 or less from which amino groups have been removed, and/or a divalent group of an aromatic diamine containing a fluorine group from which amino groups have been removed, and a combination of only a tetravalent group (A) of an aromatic tetracarboxylic acid containing no fluorine group from which carboxyl groups have been removed, and only a divalent group (B) of an aromatic diamine containing no fluorine group from which amino groups have been removed, is excluded.
 2. The aqueous polyimide precursor solution composition according to claim 1, wherein the imidazole is selected from the group consisting of 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 4-ethyl-2-methylimidazole, and 1-methyl-4-ethylimidazole.
 3. A method for producing an electrode, comprising: producing an electrode mixture paste by mixing the aqueous polyimide precursor solution composition according to claim 1 with an electrode active material; applying the electrode mixture paste onto a current collector; and then heating the electrode mixture paste to remove a solvent and effect imidization. 